Petroleum System – Source Rock Draupne Formation

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 50- 250 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 2-2.5 %

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 300-2000 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.

Petroleum System – Traps and Seals

Traps

• 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.

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

2D Cross Section Imaging

2D Cross Section Imaging

Anticline
Hanging Wall
Fault

Stratigraphic Correlation

Unconformity
Thinning Strata S-N
Thickening Strata S-N

Depositional Environment

Volumetric Estimation of Gullfaks Field

Breakdown Of STOIIP Based on Layers

Breakdown Of GIIP Based on Layers