Formation and thermal evolution of insoluble reservoir bitumen in Angolan carbonate reservoirs.

Pyrobitumen resulting from the thermal cracking of crude oil is a frequent occurrence in petroleum reservoirs. Despite the detrimental implications of pyrobitumen for the poroperm qualities of the reservoir; little is known about the evolution of pyrobitumen properties as a function of increasing thermal stress. A suite of pyrobitumen-bearing reservoir cores from the carbonate Jurassic Pinda formation in offshore Angola has been studied using geochemical and petrographic techniques (including elemental analysis, Rock Eval pyrolysis, GC, FTIR, XRD, SEM, TEM) in order to characterise the physical, chemical, and optical properties of the pyrobitumen as fully as possible. The 11 core samples contain pyrobitumen at reflectance values ranging from 0.55-2.24%Ro and display varying degrees of solubility in dichloromethane from 98% insoluble bitumen to 45% insoluble, indicating a substantial spread of maturity. However, these indicators of maturity, and further classical maturity indicators such as the H/C and Tmax show surprisingly poor mutual agreement

Pyrobitumen occurrence and formation in a Cambro–Ordovician sandstone reservoir, Fahud Salt Basin, North Oman

The Cambro–Ordovician Barik Sandstone reservoirs in the Fahud Salt Basin in Oman contain bitumen which may fill up to 40% of the porosity. In well Jaleel-1, this bitumen was isolated (according to kerogen procedure) and typed by NMR, elemental analysis and density measurements. The isolated bitumen is characterized by: (1) a highly aromatic character (NMR 75% CAro, H/C atomic ratio: 0.65), (2) a very high sulphur content (4.2%) and (3) a relatively high density (1.3–1.4 g/cm3). The insolubility and the reflectivity of the bitumen (1.2% Vr) qualify it as a low mature pyrobitumen. The combination of Rock-Eval and density data was used to calculate the actual volume of the pyrobitumen in the rock, as a percentage of porosity. It was found that the pyrobitumen volume shows a negative correlation with total porosity, indicating that small pores are more invaded by bitumen than larger ones. Finally, closed system pyrolysis experiments, performed on oils with different NSO contents, indicate that an in situ oil with a very high content of NSO compounds is required to generate such large amounts of pyrobitumen in the pore system. These observations suggest that the precursor oil of the current pyrobitumen was a very heavy oil tentatively assumed to be the result of a severe biodegradation. Basin modeling shows that the reservoir was charged already in Devonian times. A major uplift brought the oil accumulation near the surface during the Carboniferous and a rather regular burial to the present day position (4500 m, 140°C) (Loosveld et al., 1996). This scenario, involving a residence time at shallow depth, strengthens the biodegradation hypothesis. The numerical modeling, which involves the IFP kinetic model for secondary oil cracking, suggests that pyrobitumen formation is a very recent event. Inclusion of pyrobitumen particles within quartz overgrowth, containing fluid inclusions, provides an upper temperature limit for the beginning of pyrobitumen formation which comforts the result of kinetic modelling

5. Filière charbon : estimation des ressources et valorisation

Le charbon est le combustible fossile le plus anciennement utilisé. À l’heure actuelle, il est encore la deuxième source d’énergie primaire* dans le monde, derrière le pétrole mais devant le gaz naturel. L’Agence internationale de l’Énergie estime que sa consommation devrait croître de près de 2 % par an d’ici 2030 où il devrait répondre à 29 % des besoins mondiaux contre 27 % aujourd’hui. Une telle poussée du charbon sur la scène énergétique mondiale s’explique d’abord par son utilisation ma..

1. La formation des ressources fossiles

De la biomasse au kérogène Charbon, pétrole, gaz naturel, hydrocarbures de roches-mères (plus connus sous le nom de gaz de schiste et huile de schiste). Autant de vocables très familiers désignant des ressources énergétiques ayant un point commun : leur composition chimique. Leur particularité par rapport aux autres ressources géologiques ? Il s’agit de mélanges souvent très complexes de composés moléculaires riches en hydrocarbures. Sur Terre, seul un phénomène est capable de transformer les..

La formation des ressources fossiles

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Utilisation de la spectrométrie infrarouge pour l'étude des inclusions fluides des minéraux : intérêts et limites

It is possible to detect in situ the main components of fluid inclusions in a short time by infrared spectrometry : water, carbon dioxide and organic matter, as their relative proportions. On the other hand, it permits to estimate the volumetric importance of those inclusions in the mineral. The interest for crystal growth studies is drawn out, but also the limits of the method, principally related to mineral absorption in the majority of the cases (with the exception of natural halogenides) which can make the fluid inclusions spectra more difficult to study.La spectrométrie infrarouge permet de détecter in situ et rapidement la présence des principaux constituants des inclusions fluides : eau, gaz carbonique et matières organiques, ainsi que d'en estimer les proportions relatives. Elle permet, d'autre part, d'évaluer l'importance volumétrique de ces inclusions dans le minéral. L'intérêt pour l'étude de la croissance de cristaux naturels est soulignée, mais les limites de la méthode sont nombreuses, liées principalement à l'absorption intrinsèque de la grande majorité des minéraux (mis à part les halogénures naturels), dont le spectre d'absorption peut masquer une grande partie de celui des inclusions.Calas Georges, Huc Alain-Yves, Pajot Bernard. Utilisation de la spectrométrie infrarouge pour l'étude des inclusions fluides des minéraux : intérêts et limites. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 99, 2-3, 1976. Les cavités intracristallines microscopiques des matériaux de la lithosphère

Thermoréduction des sulfates dans les réservoirs pétroliers (approche moléculaire)

STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Organic geochemistry of Cretaceous black shales at DSDP Hole 75-530A

Five-hundred ten meters of Cretaceous sediments were drilled north of the Walvis escarpment in Hole 530A during Leg 75. An immature stage of evolution for organic matter can be assigned to all the samples studied. Black shales are interbedded with red and green claystone in the bottom sedimentary unit, Unit 8, which is of Coniacian to late Albian age. The richest organic carbon contents and petroleum potentials occur in the black shales. Detrital organic matter is present throughout the various members of a sequence, mixed with largely oxidized organic matter in the gray and green claystone or marlstone members on both sides. Detrital organic matter also characterizes the black streaks observed in the claystones. Vertical discontinuities in organic matter distribution are assigned to slumping. Several types of black shales can be identified, according to their content of detrital organic matter, the more detrital black levels corresponding to the Albian-Cenomanian period. Cyclic variations of organic matter observed for a sequence can occur for a set of sequences and even for some consecutive sets of sequences. Climatic factors are proposed to account for the cyclic sedimentation and distribution of organic matter for every sequence that includes a black bed