offshore geohazard site investigation
TRANSCRIPT
Offshore Geohazard Site Investigation
Seun Familusi
Upstream Oil and Gas Perspective
(Nigerian Oilfield Case Study)
What are Offshore Geohazards?
Introduction Methods Results & Interpretation Conclusion
Why is Offshore Geohazard Site Investigation Required?
Introduction Methods Results & Interpretation Conclusion
Required to obtained detailed seabed and sub-seabed information of any area where
offshore activities are to take place.
Why is Offshore Geohazard Site Investigation Required?
Introduction Methods Results & Interpretation Conclusion
Why is Offshore Geohazard Site Investigation Required?
Introduction Methods Results & Interpretation Conclusion
How is the Investigation Conducted?
Introduction Methods Results & Interpretation Conclusion
Combines the science of HYDROGRAPHY, GEOPHYSICS and GEOTECHNICS
How is the Investigation Conducted?
Introduction Methods Results & Interpretation Conclusion
DGPS Navigation & Positioning . Seabed Imaging & Shallow Geology . Ground truthing
Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Specialized Geohazard Vessel
Investigation Crew
Surveyors
Engineers
Geophysicists
Geologists
Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Differential Global Positioning System (DGPS)
Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Bathymetry (Single Beam & Multi beam Echo sounders)
Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Bathymetry (Multi beam Echo sounder)
Uneven Seafloor Topography
N
Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Seabed Features (Sidescan Sonar)
Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Seabed Features (Sidescan Sonar Record)
Barge Wreck Barge Wreck
So
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Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Seabed Features (Sidescan Sonar Movie)
Barge Wreck Barge Wreck
So
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Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Seabed Features (Marine Magnetometer)
Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Shallow Geology (Sub-bottom Profiler)
Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Two-Dimensional 2D Seismic (Streamer & Seismic Gun Source)
Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Two-Dimensional 2D Seismic (Streamer & Seismic Gun Source)
Air Gun Source
Streamer
Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Two-Dimensional 2D Seismic (Streamer & Seismic Gun Source)
Sub Surface Image
Key Tools and Equipment
Introduction Methods Results & Interpretation Conclusion
Geotechnical Investigations (Grab Samplers, Piston Corers)
Grab Sampler
Piston Corer
Equipment Interfacing & Integration
Introduction Methods Results & Interpretation Conclusion
Mobilised Geohazard Vessel
Survey Lines Design
Introduction Methods Results & Interpretation Conclusion
Survey Grid/Lines
Navigation Screen
Introduction Methods Results & Interpretation Conclusion
Online Geohazard Survey
Navigation Screen
Introduction Methods Results & Interpretation Conclusion
Online Geohazard Survey
Geohazard Site Investigation Methods
Introduction Methods Results & Interpretation Conclusion
3km by 3kmSurvey Grid
Gulf of Guinea
Niger-DeltaSedimentary BasinIn Nigeria
Purpose
FloatingProduction StorageandOffloading(FPSO)Tanker
And
Drilling Activities
Bathymetric Overview of Study Area (Single Beam)
Introduction Methods Results & Interpretation Conclusion
31 m
32 m
30 m
Bathymetric Relief of Study Area (Multi Beam)
Introduction Methods Results & Interpretation Conclusion
30 m
31 m
32 m
-25
2627
-28
29
30
-31
32
-33
-34
35
36
-37
38
39
-40
41
42
-43
44
-45
Seabed Features and Magnetic Anomaly (Sidescan Sonar & Magnetometer)
Introduction Methods Results & Interpretation Conclusion
Magnetic Anomaly
Seabed Mosaic (Sidescan Sonar)
Introduction Methods Results & Interpretation Conclusion
N
Shallow Geology (Sub-bottom Profiler)
Introduction Methods Results & Interpretation Conclusion
Unit A
Unit B
Approx. 110 m
Sandy Clayey lens
Clay Sediments
Sea Floor0-10-20-30-40-50-60-70-80-90-100-110-
Seismic Profile of the Study Area
Introduction Methods Results & Interpretation Conclusion
Approx. 100 m
Sandy Clayey lens
Clay Sediments
Shallow Gassy Channel Shallow Gassy
Channel
Gas Chimney?
Amplitude Anomalies within the Study Area
Introduction Methods Results & Interpretation Conclusion
Approx. 100 m
Sandy Clayey lens
Clay Sediments
Stratigraphic Summary from 2D Seismic Survey
Introduction Methods Results & Interpretation Conclusion
Approx. 100 m
Sandy Clayey lens
Clay Sediments
Summary of Geotechnical and Laboratory Test on Core Samples
Introduction Methods Results & Interpretation Conclusion
Approx. 100 m
Sandy Clayey lens
Clay Sediments
Conclusion
Introduction Methods Results & Interpretation Conclusion
Approx. 100 m
Sandy Clayey lens
Clay Sediments
1. Same parts of the study area are considered to be gas charged therefore any drilling activity must be avoided in these areas. The North-West and the Southern parts of the study area.
2. There is no potential risks to placing the Floating Production Storage and Offloading (FPSO) at the study area
3. The study area clear from any form of debris or obstructions.
TAKE HOME MESSAGE
Introduction Methods Results & Interpretation Conclusion
Approx. 100 m
Sandy Clayey lens
Clay Sediments
Geohazard Site Investigation is criticalto all offshore oil and gas activities
and has to be conducted prior to field operations to avoid accidents.