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Abouarkoub A.,The Libyan Petroleum Institute | Thompson G.E.,University of Manchester | Zhou X.,University of Manchester | Hashimoto T.,University of Manchester | Scamans G.,Innoval Technology
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2015

The influence of prolonged ambient temperature storage on the subsequent precipitation behavior of the AA6111-T4P automotive alloy during artificial aging has been investigated using hardness testing and high-resolution transmission electron microscopy. The results indicate that growth of atomic co-clusters and GP zones during ambient storage suppress the onset of Q′ and Q precipitation, and retard the formation of elemental silicon particles. However, the overall hardening response of the stored AA6111 T4P alloy to subsequent peak-aging and over-aging treatments is not altered by the significant reduction in the volume fraction of Q′ and Q precipitates due to their lower strengthening effects compared with GP zones and the Q″ phase precipitates. © 2015, The Minerals, Metals & Materials Society and ASM International.

Khalifa M.,Uppsala University | Khalifa M.,The Libyan Petroleum Institute | Morad S.,Uppsala University | Morad S.,The Petroleum Institute
Marine and Petroleum Geology | Year: 2012

This petrographic, mineral chemical, fluid inclusion, and stable isotopic study shows that the distribution of diagenetic modifications and their influence on reservoir quality and heterogeneity in tidal and fluvial sandstones of the Upper Cretaceous Bahi Sandstones in the rift Sirt Basin, NW Libya varies systematically along a series of closely-spaced, dominantly normal faults between the basin margin and more basinward-located areas. Shallow eogenetic modifications resulting from the percolation of meteoric waters, include infiltration of grain coating clays, kaolinitization of detrital silicates, and cementation by dolomite and K-feldspar overgrowths. Mesogenetic alterations (>70 °C, >2 km) include feldspar albitization, illitization of infiltrated clay and kaolinite, conversion of kaolinite into dickite, and cementation by quartz overgrowths (T h 112 °C-134 °C), barite (T h 145 °C-158 °C) and Fe-carbonates. The restriction of barite and Fe-carbonate cements to the basinward-located sandstones suggests formation by hydrothermal fluids along the faults. Extensive feldspar dissolution and formation of moldic pores in sandstones from the basin margin were probably caused by deep percolation of meteoric waters. Results from this study regarding the structural control on the spatial distribution of diagenetic alterations have implications for constraining the flux of pore fluids and, by extension, reservoir quality in analogous epicratonic rift basins. © 2011 Elsevier Ltd.

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