Suchergebnisse

The present work is conducted on the Paleozoic (Ordovician) Khabour and the (Silurian) Akkas shales in the Akkas-1 well of western Iraq. The study is aiming to determine the implications of clay mineral transformation, organic mineral distribution and maturity of hydrocarbon generation, using X-ray diffraction (XRD), scanning electron microscopy (SEM) in addition to organic matter concentrations. In the shale of the Khabour Formation, amorphous organic matter is common and includes various Tasmanite-type organic matter, vitrinite, inertinite, and bituminite. The main clay minerals observed include illite, chlorite, kaolinite, in addition to mixed-layer illite-smectite and rare smectite. In Silurian shale, high content of organic matter is recorded in addition to abundant vitrinite and low content of grainy organic matter (Tasmanites) and pyrite. Illite and kaolinite are commonly found in addition to chlorite and illite-smectite clay minerals. Conversion of smectite to mixed-layer illite-smectite (I-S) and an increase in vitrinite reflectance are commonly observed below 2500 m depth in the studied formations, which coincides with oil and gas generation. These results could be used as an indication of higher maturity and hydrocarbon generation in the deeply buried shale of the Khabour and Akkas formations in western Iraq.

The lithostratigraphic and biostratigraphic studies of the Shiranish Formation in the Diana area, Erbil, Northern Iraq, were conducted to distinguish the main lithostratigraphic units, depositional environment and the formation age. The Shiranish Formation in the study area can be divided into three rock units. The lower and upper units consist of marly limestone, marl and limestone deposited in the outer shelf environment, while the middle unit is dominated by laminated calcareous shale and marl deposited in the upper bathyal environment. Calcareous nannofossils showed the presence of about 20 species/genera in the studied Shiranish Formation. Three biozones are identified; Misceomarginatus pleniporus biozone; Ceratolithoides aculeus biozone, and Uniplanarius sissinghii biozone. From a regional perspective, these biozones were compared with other nannobiozones, leading to the conclusion that the studied section is of Middle Campanian age.

The early Carboniferous Harur Formation from the Ora outcrop section of northern Iraq consists of black shale, calcareous shale and carbonate. The mineralogical and geochemical investigations (major and trace elements) of the black shale and calcareous shale units have been conducted to evaluate paleoenvironmental conditions including paleoclimate, paleoredox conditions, paleoproductivity, sedimentary rate, and to evaluate their effects on organic matter accumulation. The geochemical proxies such as the Chemical Index of Alteration (CIA), A-CN-K plot, Sr/Cu ratio, and the relation between the ratio of Ga/Rb and Sr/Cu suggest moderate to intense chemical weathering under humid conditions. The Rb/K and Sr/Ba ratios indicate a freshwater environment during deposition. Multiple paleo-redox indicators such as ratios of V/(V+Ni) and Th/U) and U index indicates deposition under depleted marine oxygen conditions and consequently recording an Ocean Anoxic Event (OAE). The Th/U ratio indicates that the sedimentary rate at the lower part of the section is less than that of the upper part of the section. The terrigenous clastic input index (Ti and Al) shows that clastic input reduced from the lower to the upper section which implies that the sea level rose first lower to the upper section. Both Al and Ti have positive correlations with TOC (Total Organic Carbon) which reveal that clastic input was advantageous for OM accumulation. The high ratios of (Fe + Mn)/Ti and the presence of nacrite minerals indicate hydrothermal activity during deposition. Hence, the main control factors of OM accumulation in the black shale and calcareous shale of the Harur Formation were terrigenous clastic fluxes, in addition to paleo-redox conditions and hydrothermal activities. On contrary, paleoproductivity proxies play a relatively less significant role in OM accumulation.