Pressures
3 important questions on Pressures
Fluid Gradients and Overpressures
• No matter how high the overpressures, the slope of
fluid (or gas) gradients will not change
• An overpressured gradient will be parallel to the
non-overpressured gradient
• The slope of the gradient is determined by the
weight of the fluid
• Water gradients are ±1.03 bar/10 m
• Lithostatic gradient is ±2.3 bar/10 m
• Oil gradients are between of 0.78 to 0.93 bar/10m
• Gas gradients are between 0.23 and 0.32 bar/10m
Overpressure in The Dutch Subsurface
Increasing overpressures towards the
North because of:
– Increased thickness of Tertiary to recent
burial
– Slow dewatering towards the south and
up the section
• Other factors contributing, e.g.:
– Shaly facies of Rotliegend and
Triassic in the northern sector of the
Dutch subsurface
– Presence of sealing faults providing
pressure seals
Protected Trap Concept
If traps are connected by a continuous
aquifer, seal failure will occur first in
the shallowest trap.
Deeper accumulations are “protected”,
as the maximum aquifer pressure is
constrained by the shallowest point of
the pressure cell.
The question on the page originate from the summary of the following study material:
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