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The Triassic Main Buntsandstein play in the Dutch northern offshore

24 mei 2016

Marloes Kortekaas*, Bastiaan Jaarsma, Ulf Böker, Cas van der Kooij and Eveline Rosendaal

EBN, the Netherlands.* Corresponding author:marloes.kortekaas@ebn.nl

New prospectivity away from the main fairway

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Poster #7

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Introduction

• Renewed exploration interest in the Mid North Sea area

• New seismic data available (incl. UK)

• The Triassic Main Buntsandstein play is underexplored in the Dutch northern offshore

• Indications for local sediment provenance of Triassicsandstones in DK and UK

• This study shows new Triassic prospectivity away fromthe main fairway

• Work in progress..

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Stratigraphic subdivision of the Triassic

3 Source: van der Kooij, 2016

Main BuntsandsteinSubgroup (MBU)

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Early Triassic depositional environment

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24 mei 2016

?

Source: Southern Permian Basin Atlas

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Well locations with Sollingfluvial sands sourced fromRingkøbing-Fyn High) (Olivarius et al., 2015)

www.ebn.nl24 mei 2016

Currently no Triassic fields in DEFAB region

General perception:• Thick ZE prevents HC migration into Trias• Thinning/shaling out of sst packages towards north

Only 20 wells have been drilled in study area (17000 km2) with MBU as primary/secondary target.

11 of these wells: invalid tests of the play

Exploration history of the Triassic in the DEFAB area

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TerracubeSource palaeogeographic outlines: Southern Permian Basin Atlas

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Top Lower Volpriehausen Sst depth map - Prospectivity

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Three types of leads:

1) “classic” leads with proven types of trap, source, seal andreservoir

2) leads which may be sourcedwith HC’s via Tertiary volcanicdykes

3) leads with local reservoir provenance area

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Charge

Source rock presence / maturity discussed in separate poster presentation.

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ZE thickness (ms)

Three charge mechanisms:

• Salt windows (ZE thickness)

• Volcanic dykes

• Faults

Analysis per lead is required – in progress

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MBU gas fields UK charged via fractures near volcanic dykes (a.o. Underhill, 2009).

Tertiary dyke trend UK (Kirton and Donato, 1985)

Tertiary dyke trend UK (Underhill, 2009)

Charge via volcanic dykes

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Amplitude extraction at base Tertiary

A

A’

A A’

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Analogue field charged via volcanic dyke

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• Thick ZE: charge bypassed ZE via volcanicdykes

• Significant lateral HC migration

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Source: Southern Permian Basin Atlas

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Reservoir: typical well log response of Lower Volpriehausen Sst

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?

MBU reservoir rocks are present in most of the studyarea

Abundance and thickness of aeolian Volpriehausen Sst. decrease from south to north.

Fluvial sands with northernprovenance may have developed as reservoir in thenorthwestern area.

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A05-01, A15-01, Bertel-1

Bertel-01

• Inconsistencies in biostrat. analysis reported

• Trias-/Jurassic boundarydoubted

• redbeds in Jurassic… continental?

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Bertel-1

A15-01

A05-01

A15-01

Bertel-1

Co

asta

l/ m

arin

e?C

on

tin

enta

l?

A05-01

• Limited info on nlog

• 2016: Biostrat analyses byTNO on A05-01

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A05-01

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• Early Cretaceous – Late Jurassic strata present

• Keuper: Schilfsandstein?

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A05-01

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Schilfsandstein

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Source: Southern Permian Basin Atlas

A05-01

Carnian (Schilfsandstein) present in Dutch northern offshore

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Seal: a thin layer of Jurassic/ Cretaceous shales can seal!

• Flora field (UK) sealed bya thin layer of L Cret. marls(and chalk).

• Way forward: velocityanalysis chalk

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Source: Hayward et al. (2003)

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Conclusions

24 mei 2016

• New prospectivity away from the main fairway (see poster #7)

• Local reservoir development

• Potential for Upper Triassic reservoirs

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Work in progress

• Reservoir development - reports will be available at ebn.nl (August 2016):

• Cas van der Kooij (UU): Triassic sand development in the northern dutch offshore

• Gioia Bezemer (UU): Depositional environment (grainsize/clay mineralogy/SEM on core material and cuttings)

• Aike Vonk (UU): Provenance study (heavy mineral analyses on core material and cuttings)

• Prospect specific evaluations

• tPOS and Volumetrics

• Presentation at Geol. Soc. Conference: ‘Mesozoic Resource Potential in the SPB’ (London, Sept 2016):

The Triassic Main Buntsandstein play – New prospectivity in the Dutch northern offshore. (available at ebn.nl (Sept 2016)

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Poster #7

www.ebn.nl24 mei 2016

Thank you for your attention

More information? Contact us:

exploration@ebn.nl

Acknowledgements:Fugro and Spectrum ASA, for giving permission to show data from the DEF survey

EBN Colleagues and Ulf Böker (Panterra, reservoir development)

References:Southern Permian Basin atlas (2010)

Geology of the Netherlands (2007)

Arfai et al. (2014), Late Palaeozoic to Early Cenozoic geological evolution of the Entenschnabel, NJG

Hayward et al. (2003), The Flora Field, Blocks 31/26a, 31/26c, UK North Sea, Geol. Soc. Memoir

Olivarius et al. (2015), Provenance of the Lower Triassic Bunter Sandstone Formation, Basin Research

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