Sedimentary Basins (Part One)

1
Sedimentary Basins(Part One)
2
What are Sedimentary Basins?
Holes in the ground where sediment
accumulates Global distribution Sub-aerial and
submarine
3
Why are Basins Interesting?
Hydrocarbons Oil, Gas, Coal Ores Minerals
4
Some estimates
Liquid hydrocarbon production will peak in 10
years at 30 Billion Barrels per annum, declining
to 5 Billion Barrels per annum by the end of
the 21st Century
5
Keeping up Supply Polar Exploration?
6
Keeping up Supply Deep Water Exploration?
7
Keeping up Supply Importance of Technology
1988 and 1995 3D seismic surveys
BP Forties Field Monthly Average Oil Production
Rate
1973 Year 2003
Technologies Seismic Reflection Imaging Deep
Water drilling/production Finding Direct
hydrocarbon Indicators Extracting Mopping up the
dregs
8
Peak Oil Supply Peaks Declines Smoothly?
Technology buffers decline?
9
Why does Sediment Accumulate Here?
10
Basins form through Tectonic Subsidence
Accommodation Space Sea-Level Change Tectonic
Uplift / Subsidence
11
Worlds Thickest Sediment Accumulations
Thickest sediment accumulations are 15 to 20
km Tend to form in enclosed basins supplied by
major rivers
12
Sedimentary basins around Ireland
13
Probing Sedimentary Basins

• Surface sampling and mapping
• Topography and bathymetry
• Boreholes (lt5 km)
• Seismic experiments (2D, 3D, 4D)
• Earthquake analysis

Undeformed basins are subsurface
14
Very little of a typical underformed basin is
accessible by surface sampling / mapping
15
Seismic Reflection Imaging
Ninian Fault Block, North Sea vertical
exageration x3 to x4
16
Seismic Reflection Imaging Technology
17
Borehole Records 1. Thicknesses 2. Ages 3.
Sediment Composition Reconstruct sediment
acccumulation history Hence reconstruct tectonic
subsidence history
18
Stratigraphic Growth
19
(No Transcript)
20
Sediment Loading Correction
21
Tectonic Subsidence Curves
22
Basin Classification Process
Basin Analysis, Allen Allen, Chapter 1
23
Basin Classification This Course

• Extensional basins (60-70)
• Flexural or foreland basins (10-20)
• Basins associated with subduction zones
• Other basin types