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Ecole Polytechnique, Montreal (1992)

Etude multidisciplinaire d’un bassin saharien pres d’In-Salah (Algerie) : Apport de la magnetotellurique

Bouzid, Abd-Errezak

Titre : Etude multidisciplinaire d’un bassin saharien pres d’In-Salah (Algerie) : Apport de la magnetotellurique

Auteur : Bouzid, Abd-Errezak

Université de soutenance : Ecole Polytechnique, Montreal

Grade : M.Sc.A. 1992

Résumé
The objective of this work is dual : (1) we want to study the upper mantle anomaly located beneath the southern Sahara (Algeria) and characterized by high heat flow, negative gravity and reduced seismic velocities between 50 and 150 km ; (2) we want to test the potential of magnetotellurics (MT) for oil and gas exploration. In January 1991, we completed a north-south profile along the 3 degrees E meridian between parallels 24 N and 30 N. This profile includes 11 soundings, 8 of which are located on the Sahara basin. The results suggest a very resistive upper crust under the northern flanc of the Hoggar massif. This upper crustal resistivity slightly decreases under the Sahara. The lower crust and upper mantle seem to be anomalous under the whole region. The conductivity increases at approximately 17 km under the northern flanc of the Hoggar and probably under the Sahara basin. Contrarily to what is generally observed in other cratons, it does not appear to decrease at greater depths. Its lateral extent are not well defined but could lie to the north of the Sahara and to the south of the southern end of our profile. The sedimentary basin is globally conductive. Its apparent resistivity essentially depends on the presence of salted formation waters. The MT results, combined with those of seismic reflection, have defined the depth extent of the Ordovician, an important formation for exploration. Our study shows that MT can be used in oil or gas exploration as an indirect tool to detect layers rich in formation water or, occasionally, depth to the basement

Mots clés : Applied sciences, Geophysics, Mining, Earth sciences

Présentation (Amicus)

Page publiée le 10 février 2015, mise à jour le 2 février 2018