1,721,016 research outputs found
Quartz cementation in Cretaceous and Jurassic reservoir sandstones from the Salam oil field, Western Desert, Egypt: constraints on temperature and timing of formation from fluid inclusions
No full textHydrothermal dolomitization in the Upper Triassic Ghalilah Formation, North-eastern United Arab Emirates
No full textDiagenesis of the Permo-Triassic rock sequence of northern U.A.E.: Lessons learnt from Khuff Formation analogues
No full textDiagenesis and Reservoir Quality Evolution of the Permian Bih Formation (Khuff Reservoir Analogue), Ras Al Khaimah, United Arab Emirates.
No full textDiagenesis of the Permo-triassic Succession of the Northeastern UAE, an Outcrop Analogue of the Khuff Formation
No full textDiagenesis and Fluid System Evolution of the Khuff Formation Outcrop Analogues, Northern United Arab Emirates
No full textFracture mineralization and fluid flow evolution: an example from the Permian-Triassic carbonate successions of United Arab Emirates
No full textFractures are often the primary conduits for pore fluids, and thus have an important impact on the diagenetic and reservoir quality evolution of the host rocks. Therefore, fluid flow can be used to
develop conceptual models for the spatial and temporal distribution and connectivity of reservoir porosity and permeability on a regional and basinal scale. In the context of the hydrocarbon-rich Middle East, the Permian-Triassic Khuff Formation hosts huge gas accumulations in the subsurface of the Arabian Plate. Reservoir properties of this formation are strongly influenced by depositional facies and diagenetic evolution (Ehrenberg et al., 2007; Fontana et al., 2010; Moradpour et al., 2008). In the Emirate of Ras Al Khaimah (RAK), in the northeast of the United Arab Emirates (UAE), there are excellent outcrops of the Permian-Triassic rock sequence, which is partly correlatable with the Khuff Formation (Strohmenger et al., 2002; Maurer et al., 2008, 2009). In this study, which involves fieldwork,
petrographic, fluid inclusion and isotope (0, C and Sr) investigations, outcrops of Permian-Triassic carbonate rocks have been studied to relate fracture mineralization to tectonic history of the area
Diagenesis of the Khuff Formation (Permian–Triassic), northern United Arab Emirates
No full textThis diagenetic study (including fieldwork, petrographic, fluid inclusion, and stable isotope investigations) deals with the outcrop of Upper Permian–Lower Triassic carbonate rocks, which are equivalent to the Khuff Formation. The studied succession, which outcrops in the Ras Al Khaimah region, northern United Arab Emirates, comprises three formations, including the Bih, the Hagil, and the Ghail formations. The study focuses on unraveling the conditions and fluid compositions encountered during diagenesis of the succession. Emphasize is also made on linking diagenesis to major stratigraphic surfaces and to highlight reservoir property evolution and heterogeneity of the studied rocks. The evolution of fluids and related diagenetic products can be summarized as follows: (1) formation of near-surface to shallow burial, fine-crystalline dolomite (dolomite matrix) through pervasive dolomitization of carbonate sediments by modified marine pore waters; (2) formation of coarse-crystalline dolomite cement by highly evolved marine pore waters (13–23 wt.% NaCl eq.) at elevated temperatures (120–208°C), and (3) calcite cementation by highly saline fluid (20–23 wt.% NaCl eq.) at high temperature (170–212°C). A final calcite cement generation has been formed by the percolation of meteoric fluids during uplift. Fracture- and vug-filling diagenetic minerals are mainly restricted to the mid-Bih breccia marker level, suggesting preferential focused fluid flow through specific stratigraphic surfaces as well as along tectonic-related structures. Reservoir properties have been evolved as result of the interplay of the original sedimentary texture and the diagenetic evolution. Porosity is higher in the Bih Formation, which is dominated by dolomitized packstones and grainstones, than in the Hagil and Ghail formations, consisting mainly of dolomitized mudstones and wackestones. Image analyses were used to quantify the visual porosity in thin sections. The highest porosity values were measured in the Bih Formation, which is characterized by significant amounts of vug- and fracture-filling cements. This feature is attributed to the increase of porosity owing to substantial dissolution of abundant intergranular and vug-filling cements. In contrast, the Hagil and Ghail formations, which consist of finer-grained rock than the Bih Formation, were less cemented, and thus, the porosity enhancement by cement dissolution was insignificant
Quartz Cementation in Cretaceous and Jurassic Reservoir Sandstones from the Salam Oil Field, Western Desert, Egypt: Constraints on Temperature and Timing of Formation from Fluid Inclusions
No full textMiddle Jurassic and Lower Cretaceous reservoir sandstones in the Salam oil field (in Egypt's Western Desert), are mostly quartz-arenites with abundant quartz overgrowths. Most overgrowths precipitated relatively early in the diagenetic history, only pre-dated by mechanical- and minor chemical compaction. Integration of the diagenetic sequence with the geological and maturation history of the basin, indicates that quartz cementation occurred prior to oil filling the reservoirs during the Eocene, probably during the Late Cretaceous, related to high subsidence and heating rates. Homogenization temperatures (Th) of aqueous fluid inclusions that occur along the boundary between the detrital quartz grains and their overgrowths indicate that the quartz cements started to grow at temperatures from about 116°C to 135°C. These palaeotemperatures are similar to, or slightly higher than, present-day formation temperatures, and show a positive correlation with present depth of burial. The palaeotemperatures obtained from fluid inclusions are higher than predicted from thermal history models. There are several possible explanations for these relatively high palaeotemperatures: (i) the Late Cretaceous burial depths were higher than initially presumed; (ii) the Late Cretaceous palaeogeothermal gradients were considerably higher than present gradients; (iii) migrating hot fluids were responsible for the growth of quartz cements, at temperatures above those resulting from the contemporary conductive geothermal gradient; or (iv) fluid inclusions were trapped at lower temperatures and re-equilibrated during subsequent burial. Although thermal re-equilibration of the grain-boundary fluid inclusions is hypothetically possible, and would resolve the inconsistencies between Th data and the thermal and migration histories, there is no clear evidence supporting re-equilibration, given the narrow ranges of Th in each sample and the lack of a correlation between Th and parameters such as inclusion salinity or size.Dirección General de Investigación Científica y TécnicaDepto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEpu
Breccia beds in the Khuff (Permian-Triassic) in Ras Al Khaimah, United Arab Emirates: collapse or transgressive origin?
No full textThe laterally extensive, so-called mid-Bih breccia beds occur in carbonate su ccess ions of the Upper Permian-Lower Triassic Khuff-equivalent Bih Formation in Ras Al Khaimah, United Arab Emirates
(UAE). These carbonates have been deposited on a stable platform setting at the passive margin of the Neo-Tethys Ocean. The breccia beds have previously been interpreted to be formed by dissolution
of sulphate beds by groundwater followed by collapse of overlying carbonate beds (Strohmenger et al., 2002; Fontana et al., 2010). Contrary to this earlier interpretation, we present several lines of field, petrographic, isotopic and fluid inclusion evidence suggesting that the "breccias" are intraformational conglomerates representing a major marine transgressive surface
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