In well cementing, the cement slurry is exposed to the conditions far different than those of ordinary Portland cement (PC) used in construction. After placement, hardened cement paste should preserve integrity and provide zonal isolation through the life of the well. American Petroleum Institute (API) Class G cement is the most common cement type used in various well conditions. Class G cement has a high degree of sulfate resistance which makes it more stable than PC when subjected to the compulsive well conditions. Ground granulated blast furnace slag (GGBFS) blended cement has a long history of use in the construction industry, but is not extensively used in well cementing applications. This study presents an experimental program to investigate the applicability of CEM I and GGBFS blended cement pastes in the well cementing industry. Class G cement and blends of CEM I and GGBFS with the proportions (80:20), (60:40), (40:60) and (20:80) are prepared with same water/cement ratio (0.44) as restricted for Class G cement in API Specification 10A to be tested. The cement pastes are cured for ages of 1 day, 7 days and 28 days at 80

Les découvertes de traces de vie primitive, fossiles et biosignatures, suggèrent que celle-ci serait apparue il y 4,3 à 3,7 milliards d’années. Cette émergence est le résultat d’étapes menant des plus simples molécules organiques aux premières formes de vie unicellulaire.Ce travail de thèse examine l’hypothèse de l’apparition de la vie dans un environnement hydrothermal, dans lequel la pression, les gradients de température et de pH, la diversité des surfaces minérales et l’abondance d’énergie chimique auraient permis l’accumulation et la complexification de la matière organique. Il s’intéresse particulièrement aux étapes de concentration des nucléotides et de polymérisation des acides aminés, respectivement briques élémentaires du matériel génétique et des protéines, inhérentes au vivant.Cette thèse présente d’abord une étude des interactions de surfaces entre nucléotides en solution et minéraux en feuillets en conditions contrôlées de température, de pH et de salinité. Dans une deuxième partie, elle récapitule les résultats obtenus par l’observation in situ de l’effet des conditions hydrothermales et des surfaces minérales sur la polymérisation des acides aminés non activés.Ce travail suggère que les minéraux en feuillets, et plus particulièrement les argiles gonflantes, augmentent la concentration locale en nucléotide de trois ordres de grandeurs au moins en présentant un comportement très dépendant des conditions physicochimiques du milieu. De plus, il reconfirme l’importance de la température dans la polymérisation des acides aminés en solution, mais montre également que la pression et la présence de surfaces minérales ont une influence majeure sur la réactivité de ces molécules. Les environnements hydrothermaux semblent donc favorables à la concentration, la préservation et la complexification de la matière organique, étapes essentielles à l’émergence des propriétés du vivant. / The discovery of traces of primitive life, such as fossils and biosignatures, suggests that life may have appeared some 4.3 to 3.7 billion years ago. This emergence resulted from a chemical evolution with steps leading from simple organic molecules to the first single-celled organisms.This thesis tests the hypothesis of a hydrothermal origin of life. In such geochemical settings, pressure, temperature and pH gradients, mineral surfaces diversity and abundant chemical energy would have favored the accumulation and complexification of organic matter. This work focuses on the concentration of nucleotides and the polymerization of amino acids, which are the building blocks of genetic material and proteins, respectively.The first part of this thesis presents a large study of the interactions between nucleotides in aqueous solutions and phyllosilicates under controlled conditions of temperature, pH and salinity. The second part describes an in situ study of the effects of hydrothermal conditions and mineral surfaces in the polymerization of non-activated amino acids.This work suggests that sheet minerals, and especially swelling clays, increase the local concentration of nucleotides by three orders of magnitude and exhibit an adsorption behavior that is very dependent on the physical and chemical conditions of the environment. Moreover, this work confirms that the polymerization of amino acids in aqueous solutions is sensitive to temperature and it also underlines that pressure and mineral surfaces have a major role on the reactivity of these molecules. Hydrothermal environments thus favor the concentration, preservation and complexification of organic matter. These are crucial steps for the emergence of the properties of life in the chemical evolution.