The Paleocene submarine fans of the Central Graben represent important petroleum reservoir units recording the cyclic input of sand-rich turbidity flows into the post-rift basin. Provision of extensive seismic (a subset of ~l5000 km" of the PGS Central North Sea MegaSurvey), well (n = 549) and core (n = 28, totalling ~2760 feet/84l m) datasets by Shell UI Europe enabled a regional-scale re-evaluation of these deposits. This thesis presents new models illustrating the distribution and quality of the Maureen and Lista Formation sandstones and the syn- and post-depositional controls on these deposits. The Lista Formation sandstones occur within northwest (channelised, proximal, ~300 feet net) to southeast (sheet-like, distal, ~50 feet net) trending (axial) fans with western/eastern fairways and minor sidefan sedimentation (west/east). Four sand-rich to sand-poor facies are defined, with distinct grain size distributions. Mean grain size is the main control on porosity and permeability. Progradation occured between the Ll and L2 units with retrogradation in the L3. This variability, and internal porosity trends, is linked to global sea level change. Characterisation of the Maureen Formation sandstones is complicated by the presence of variable chalk facies derived from turbidite, debris flow and pelagic processes. However, these deposits can still be classified in a similar manner to the Lista Formation and exhibit similar spatial distributions, although the sandstones are thinner ~125 feet in the northwest to 25 feet in the southeast, suggesting that similar depositional controls were active. Sandstone quality is controlled by grain size (with calcitisation also important) although the porosity/permeability values are lower than in the Lista Formation. Progradation occured between the TlO and T20/30 sequences with retrogradation in the T35. The current MlIM2 divisions do not describe the complexity of this formation. The routing of the sandstones was defined by the relict graben structure with offset stacking an additional local control. Routing from the shelf to the basin was controlled by global sea level change. Although these systems are often labelled as basin floor fans they do not resemble classical examples, thanks to their confined nature.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:558597 |
| Date | January 2011 |
| Creators | Kilhams, Ben A. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=186272 |
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