Upper Jurassic sandstone reservoir quality and distribution on the Fladen Ground Spur

During the Oxfordian to Early Kimmeridgian much of the Fladen Ground Spur was a positive feature and sourced clastic deposition in the Piper Basin, Witch Ground and South Viking grabens. The eudoxus flooding event introduced shallow marine conditions onto the Fladen Ground Spur, and during the continuing transgression, a veneer of clastic sediments was deposited. Three facies units are defined: facies 1 - thin, low-high-energy glauconitic sandstone; facies 2 - medium-high-energy clean, well-sorted medium-grained sandstone; facies 3 - low-energy, fine-grained argillaceous sandstone. Reservoir quality is evaluated using porosity data from neutron porosity and bulk density logs. Porosity-permeability cross-plots provide a workable relationship for permeability prediction in uncored wells. Initial results show that, predictably, facies 2 sandstone has the best poroperm characteristics. Facies 1 sandstone contains locally derived clasts, the diverse nature of which affects reservoir quality. Subcrop is interpreted to be an important, if not causal, factor that controls reservoir quality in facies 1 sandstone.