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Advancements and Learning in Hydrocarbon Seep Hunting as a Critical Tool for Early-Stage Oil and Gas Exploration Bryan Bergkamp AOG 2019
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Summary
▪ What is a seep?
▪ Seep hunting
▪ An iterative process of collecting and interpreting geophysical data to identify the best sites for geochemical sampling
▪ Seafloor mapping and target selection
▪ Seafloor sampling
▪ Shipboard geochemistry
▪ Benefits of shipboard geochemical analysis
▪ Comparison of shipboard and shore based headspace gas chromatography analysis
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Introduction to Seeps
▪ Faults extend from the reservoir interval to near the seafloor
▪ Shallow amplitude anomalies and seafloor mud mounding suggest the potential for hydrocarbon seepage
▪ Hydrocarbon signal at the seafloor can give information about the reservoir before exploration drilling
▪ Thermogenic vs. biogenic gas
▪ Reduced drilling risk
Seep
Salt
3-D Exploration Seismic Data
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Seep Hunting Overview
Seafloor Mapping
Multibeam Echo Sounder Data
• Bathymetry
• Backscatter
• Water Column Seafloor Sampling
• Piston Core
• ROV
Frontier Areas
Exploration
2D and 3D
Seismic Data
Third Party
Shore Based
Geochemistry
Laboratory
Advanced Screening
Integrated Data
Deliverable & Report
Heat flow, metocean, environmental baseline, towed camera
Survey Planning Offshore Seep HuntAdvanced Geochemical
Laboratory
Shipboard Geochemistry: Standard Screening
• Headspace Gas Chromatography C1-C5
• Total Scanning Fluorimetry (TSF)
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Seep Hunting Overview
Seafloor Mapping
Multibeam Echo Sounder Data
• Bathymetry
• Backscatter
• Water Column Seafloor Sampling
• Piston Core
• ROV
Heat flow, metocean, environmental baseline, towed camera
Survey Planning Offshore Seep HuntAdvanced Geochemical
Laboratory
Shipboard Geochemistry: Standard Screening
• Headspace Gas Chromatography C1-C5
• Total Scanning Fluorimetry (TSF)
Third Party
Shore Based
Geochemistry
Laboratory
Advanced Screening
Integrated Data
Deliverable & Report
Frontier Areas
Exploration
2D and 3D
Seismic Data
www.fugro.com6
Simplified Geochemical Analysis Progression
Standard Screening
• Headspace Gas Chromatography
• Total Scanning Fluorimetry
• Liquid extract GC analysis C15+
Advanced Screening
• Biomarkers
• Extractable Organic Matter (EOM)
Integrated Data
Deliverable
• Isotopes
• DNAFewer Samples
Higher Cost
More Samples
Lower Cost
Shore Based
Laboratory
Shipboard or
Shore Based
Laboratory
Reporting
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Schedule Comparison
Offshore CampaignStandard Screening
Advanced Screening
Integrated Data Deliverable & Report
Select samples
Without Shipboard Geochemistry
Offshore CampaignStandard Screening
Advanced Screening
Integrated Data Deliverable & Report
Standard screening
for all samples
With Shipboard Geochemistry
Shore Based Laboratory
Shore Based Laboratory
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Survey Vessel Selection
▪ Hull-mounted multibeam echo sounder
▪ Sub-bottom profiler
▪ A-frame for piston coring
▪ Deck space for geochemical sampling laboratory containers or internal lab space
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Seafloor Mapping
Before the wide use of seafloor imaging,
offshore seep hunting in frontier areas was
performed by acquiring seafloor samples in
a regularly spaced grid.
Point-source hydrocarbon seeps may be
missed by grid sampling.
High-quality multibeam echo sounder
seafloor mapping is used to “hunt” for
seeps so they can be accurately sampled.
Property of NIWA LTD 2005 all rights reserved (reference 11-20859.tif).
Multibeam echo sounder seafloor mapping
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Anatomy of a Hydrocarbon Seep
▪ Quality seeps yielding positive geochemical signals are focused point sources on the seabed
▪ Upwelling fluids, react with shallow pore fluids to create carbonate nodules, chimneys, slabs, and mounds at and below the seafloor
▪ Chemosynthetic organism communities use seeping hydrocarbons as energy
▪ Seepage velocities ranged 3 cm/yr. at the seep to 0.2 cm/yr. at 80 m from the seep
▪ Missing the target by tens of meters can yield inconclusive geochemical signal
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Multibeam Echo Sounder Seep Hunting
Bathymetry
Backscatter
Water columnResult
Stacked view
Fan view
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Seafloor Sampling using Six-Meter Piston Core
Real time tracking
20 m
Corer
deployedCorer in
seafloor, after
navigating
with target
range
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1
5
1
5
1
11
1
1
1
15
1
1
1
1
1
Sub seafloor
depth m
Section
Can B
Can A
Bag A
Bag B
Archi e
Archi e
Archi e
OnboardC1 C gaschromatographysample
OnboardC1 C gaschromatographysample
OnboardC1 C gaschromatographysample
Archi e
Archi e
Archi e
Seafloor stratigraphy
5
1
15
5
cm
Stratigraphy
Discarded
Discarded
Onboardsol ent extractablefluorescencespectroscopysample
Shore basedanalysis
Shore basedanalysis
Geochemical Sub-Sampling
Headspace Gas
Fluorimetry
Samples for Shore Based Analysis
Archives
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Shipboard Geochemical Analysis Total Scanning Fluorimetry
▪ Shipboard geochemistry has wider use in academia, but limited commercial use
▪ Total scanning fluorimetry results are ready within 48 hours of sample acquisition
▪ Shipboard TSF results qualitatively correlate with shore based TSF results
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Shipboard Geochemical Analysis Gas Chromatography
▪ Headspace gas chromatography results are ready within hours of sample acquisition
▪ Identifies samples with potential for thermogenic gas indicators (contain high proportion of C2+, propane, butane, etc.)
Headspace gas is the gas above the
sample. It contains volatile organic
components released from the
sample.
These components are analyzed
with gas chromatography.
Headspace
gas
Sample
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Headspace Gas Concentration Correlation
▪ 2,000 samples analyzed and compared
▪ Fugro shipboard laboratory
▪ Four shore based laboratories
▪ In general samples compare very well
▪ For samples near background level, shore based laboratory analysis generally yielded lower headspace gas concentrations as compared to shipboard analysis
1
10
100
1000
10000
100000
1000000
1 10 100 1000 10000 100000 1000000
Fugro
Meth
ane p
pm
V log
Shore based Methane ng/g log
Methane (ppm)
1
1
1
1
1
1
1
1 1 1 1 1 1
Fugro ppm rd arty ng g
Total alkanes C
1to C
Thermogenic Biogenic ratio C1 C
+C
Background
Thermogenic ixed Biogenic
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Summary of Shipboard Geochemical Analysis
▪ Geochemical results are used in the field to guide the seafloor sampling program
▪ Headspace gas chromatography results ready within hours
▪ Total scanning fluorimetry results ready within 48 hours
▪ Identify samples in the field with potential for thermogenic gas indicators(thermogenic vs biogenic source)
▪ Analyses are performed for all samples giving a complete standard screening dataset
▪ Reduced time of shore based laboratory program
▪ Less risk of sample degradation during transit to shore based laboratory
▪ Optimize time and cost of program
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Thank you
Bryan Bergkamp
Seep Hunting Technical Lead Asia Pacific
08 6477 [email protected]