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

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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 4518bbergkamp@fugro.com