Geology topics
Source-linked reports with geographic coverage including Algeria.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 80.1 trillion cubic feet of shale gas in the Grand Erg/Ahnet Basin Province of Algeria.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 30.5 trillion cubic feet of tight gas in the Grand Erg/Ahnet Province of Algeria.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 378 million barrels of oil and 7 trillion cubic feet of gas in the Grand Erg/Ahnet Province of Algeria.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 1.3 billion barrels of oil and 63 trillion cubic feet of gas in the Reggane Basin Province of Algeria.
The Algerian Geological Survey Agency – U.S. Geological Survey (ASGA-USGS) mineral resource assessment project in the Eglab region, Algeria, comprises the eastern part of the Reguibat Shield bounded by the Tindouf, Reggane, and Taoudeni basins to the north, east, and south, respectively. The use of mobile GIS applications on handheld tablets facilitated team coordination and ease of transition from field planning and preparation, data collection and integration, and transfer back into project GIS databases. Mobile GIS applications facilitated collaboration between teams collecting disparate data types to support the geologic, geochronological, geochemical, field spectral, and geophysical investigations. This technology was used in parallel with the traditional field investigation methods. These tailored applications on GPS-enabled tablets provided a platform for utilization of GIS data in the field and allowed for standardized data collection, picklists, fewer transcription errors, and the ability to store photos, coordinates, and field notes together in an integrated system. The suite of Environmental Systems Research Institute, Inc. (Esri™) mobile applications allowed for customized use on multiple platforms (Android/Windows/iOS) to streamline data collection, analysis, and storage.
The ability to distinguish crude oils generated from prolific Silurian and Devonian source rocks provides a means to map their petroleum systems and thereby reduce exploration risk in North Africa. Routine geochemical analyses commonly fail to reliably separate these oils. This study demonstrates that non-routine analyses, such as compound-specific isotopes of light hydrocarbons and gas chromatography-mass spectrometry of diamondoids, can distinguish Silurian from Devonian oils in Algeria. Oil samples from Zemlet field and the giant Hassi Messaoud field were obtained from the northern part of the study area in Algeria where the Devonian source rock is absent. These oils originated from thermally mature Silurian source rock and migrated updip to fractured Cambro-Ordovician quartzite reservoirs below the Hercynian unconformity. Oil samples from the Assekaifaf, Oued Zenani, Zarzaitine, and Dome fields occur in the southern part of the study area, where both source rocks exist, but migration paths indicate input mainly from Devonian source rock. Despite higher maturity, the Silurian oil samples have diamondoid isomer concentrations 2–3 times lower than the Devonian samples. Because diamondoids form in source rocks by clay-catalyzed reactions and increase relative to other compounds during thermal cracking of oils, the diamondoid concentrations in the oil samples suggest that the Silurian source rock had less clay than the Devonian source rock. Higher dibenzothiophene/2-methylnaphthalene and generally higher sulfur in the Silurian oil samples support a source rock with less clay. For the Devonian oil samples, slightly more iron in clays reacted with sulfides to form pyrite, thus limiting sulfur incorporation into the kerogen and the generated crude oil. Light hydrocarbons, such as n -hexane, methylcyclopentane, cyclopentane, and methylcyclohexane, are depleted in 13 C in the Silurian compared to Devonian oil samples (> 1.1,0.6, 1.0, and 0.2 respectively). Patterns of isotopic ratios among these compounds also differ ( e.g. cyclohexane is more depleted in 13 C than methylcyclopentane and methylcyclohexane in Silurian, but not Devonian oil samples). The Silurian oil samples have smaller differences in δ 13 C between pristane and the C 17 n -alkane and between phytane and the C 18 n -alkane than the Devonian samples. Different assemblages of organisms likely contributed to the acyclic isoprenoids versus n -alkanes in the source rocks for these two oil families.
No abstract available.