Late Neoproterozoic to early Cambrian intra-salt Ara reservoirs of the South Oman Salt Basin represents a unique self-charging petroleum play with respect to hydrocarbon and overpressure generation and dissipation. Reservoir bodies (termed 'stringers') are isolated in salt and frequently contain low-permeable dolomites that are characterized by high initial production rates because of hard overpressures. A database of more than 30 wells has been utilized to understand the distribution and generation of overpressures in intra-salt reservoirs that can be separated by up to 350 m of salt. A temporal relationship of increasingly overpressured reservoirs within stratigraphically younger units is observed, and two distinctly independent trends emerge from the Oman dataset; one hydrostatic to slightly above hydrostatic and one overpressured from 17 to 22 kPa m )1 , almost at lithostatic pressures. Structural, petrophysical and seismic data analysis suggests that overpressure generation is driven by fast burial of the stringers in salt, with a significant contribution by thermal fluid effects and kerogen conversion. Structural and geometric information indicates that present-day hydrostatic stringers have been overpressured in their earlier geologic evolution. Evidence for these initial overpressures in currently hydrostatic reservoirs is provided by hydrocarbonveined cores from halite overlying the reservoirs. A proposed pressure deflation mechanism can be related to the complex interplay of salt tectonics and fast deposition of early Cambrian to Ordovician age clastics.

Large rock inclusions are embedded in many salt bodies and these respond to the movements of the salt in a variety of ways, including displacement, folding and fracturing. One mode of salt tectonics is downbuilding, whereby the top of a developing diapir remains in the same vertical position, while the surrounding overburden sediments subside. We investigate how the differential displacement of the top salt surface caused by downbuilding induces ductile salt flow and the associated deformation of brittle stringers, by an iterative procedure to detect and simulate conditions for the onset of localization of deformation in a finite element model, in combination with adaptive remeshing. The model setup is constrained by observations from the South Oman Salt Basin, where large carbonate bodies encased in salt form substantial hydrocarbon plays. The model shows that, depending on the displacement of the top salt, the stringers can break very soon after the onset of salt tectonics and can deform in different ways. If extension along the inclusion dominates, stringers are broken by tensile fractures and boudinage at relatively shallow depth. Spacing of the boudin-bounding faults can be as

We combine 1 H, 7 Li, and 19 F NMR methods to selectively investigate polymer, cation, and anion dynamics in polymer electrolytes on various length and time scales and over broad temperature ranges. By mixing unentangled poly(propylene glycol) (PPG) with lithium perchlorate (LiClO 4 ) or lithium bis-(trifluoromethylsulfonyl)imide (LiTFSI), fully disordered samples are obtained at all studied concentrations. In static field gradient diffusometry, we observe that the longrange motion of all components slows down when the salt concentration is increased, but the effect is more prominent for PPG−LiClO 4 than PPG−LiTFSI electrolytes and, in general, differs for the respective components. The self-diffusion coefficients D of polymer and ions have essentially temperature-independent ratios, where cations are less mobile than anions and do not show Arrhenius temperature dependence. To ascertain short-range motions in broad dynamic ranges, spin−lattice relaxation studies, including field-cycling relaxometry, are combined with stimulated-echo experiments. We show that rate and heterogeneity of local lithium and polymer dynamics depend on the salt content. For intermediate salt concentrations, the segmental motion even exhibits bimodal distributions of correlation times τ, implying structures with salt-rich and salt-depleted regions. Relating diffusion coefficients D and correlation times τ, we find that the lithium ion transport is strongly coupled to polymer segmental motion even in polymer electrolytes with micro-heterogeneous salt distributions. Finally, field-cycling susceptibilities reveal that Rouse dynamics is important not only for the reorganization of polymer chains but also for the transport of lithium ions.

No abstract

No abstract