مشروع البحث: Structural evolution and fluid flow analyses of the Wessex Basin, south-UK
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المساهمين
الممولين
رقم التعريف
368
الباحث
Mohamed Seddik Benshatwan
الوصف
The salinity measurements of the aqueous fluid inclusions were classified into low
salinity group (≤3.5 wt % NaCl) and moderate to high salinity group (>3.5 - 25.0
wt % NaCl). Fluid inclusion salinities indicate that the elevated amount of
dissolved NaCl, in the water that led to vein growth, is related to proximity to
halite-bearing evaporites (although doubtless other factors may have had an
additional control such as full-geometry of fault systems). The vein salinity
integrated with the interpreted values of water 18O revealed the origin of the water
and hence revealed fluid movement patterns in the basin. The indication of high
salinity and relatively low 18O-water in veins in the Blue Lias, Beacon Limestone
and Frome Clay Formations, in the area west of Portland, reveals that meteoric
water penetrated down to Mercia halite-rich evaporites probably during basin
structural inversion and then into the overlying Lower and Middle Jurassic. The
similarity of geochemical signatures of these fluids with early Cenozoic oil-field
formation water in Lower Triassic reservoirs, found in the eastern part in the basin,
emphasises there was a large scale fluid movement (open fluid flow system). In
contrast, low salinity and relatively high 18O-water in veins in the Lulworth,
Durlston and Chalk Formations, in the area east of Portland, were probably derived
from marine connate water (suggesting a relatively closed diagenetic system with
little fluid flow). This connate water was diluted by very low salinity-high 18O
water, possibly from various diagenetic dehydration reactions during burial and
diagenesis. The association of relatively high salinity and high 18O-water from
the Kimmeridge and Upper Greensand veins suggest mixing of both previously
mentioned water sources (mixed open and closed diagenetic systems).
It seems that there is no simple relationship between fault systems and the vein
microstructures and geochemistry. However, the presence of oil inclusions in late
Cretaceous E-W reactivated fault, at a considerable distance from the source
الكلمات الدالة
kitchen, implies that these faults have acted as a conduit for oil migration probably during the late Cretaceous-early Cenozoic inversion event. The considerable flux