1. Petroleum System – Source Rock
Draupne Formation
Main Shale rock that forms the hydrocarbon source in this field
Physical Characteristics Include
Brownish Black
Medium of Dark Olive Grey
Non- Calcareous Mudstones
Thickness of Formation typically m but may exceed 1200m in localized area
Heather Formation
Dark grey Silty Mudstones with thin Carbonate layers
Thickness formation ranges up to 1000 m
It is typically gas prone
Total organic carbon ( TOC ) values are typically between %

2. Petroleum System – Reservoir Rock
Triassic and Lower Jurassic
Occurs in tilted fault blocks with varying degree of Jurassic
Cretaceous erosion and onlap.
The main reservoir intervals comprise of thick , fluvial channel and sheetflood deposit.
Porosity range from 20-24%
Permeability mD
Middle Jurassic
Present in the Northen Sea are arkoses and subarkoses with quartz , clay minerals and Fledspars consisting about 95 % of the total miner
Sandstones are both quartz and calcite cemented at depths exceeding 2500 m.
Reservoir form a thick clastic wedge comprising laterally extensive interconnected fluvial
Deltaic and coastal depositional systems with porosities 20-30% and permeability 50 – 500 mD.

3. Petroleum System – Traps and Seals
Most trapping mechanism is provided by rotated faults sealed by fine grained post rift sediments.
Seals
These sediments draped on to the structures to form seals
Lateral trapping and sealing is formed where reservoir rocks are juxtaposed with non-reservoir rocks at fault contacts
Most seals are closed to hydraulic fracture.

4. Petroleum System – Migration
Migration Mechanism
Primary migration - Pressure driven flow of a discrete hydrocarbon phase through pores and micro fractures
Secondary migration - Buoyancy resulting from difference in density between the hydrocarbon and water

5. 2D Cross Section Imaging

6. 2D Cross Section Imaging
Anticline
Hanging Wall
Fault
The structure shows a fault as indicated by the arrow and the existence of anticline, which makes it a suitable hydrocarbon reservoir trap. This 2D cross imaging will be compared to the static model that will be explained in the next section for accuracy comparison.

7. Stratigraphic Correlation
Unconformity
Thinning Strata S-N
Thickening Strata S-N

8. Depositional Environment

9. Volumetric Estimation of Gullfaks Field

10. Breakdown Of STOIIP Based on Layers

11. Breakdown Of GIIP Based on Layers