oil&gas thought-leader webinar - new plays for old ideas - dr. rob forkner

Why we must consider OAEs whenexploring Mesozoic systemsRob Forkner, Statoil Exploration Research Center Austin 13 March 2017Classification: Internal

© Statoil ASA

Why should industry care about OAE?• Source Rock: Improving 2D/3D facies mapping within SR intervals. OAE and

unique biomarker/diamondoid fingerprinting?

• Reservoir: Improving understanding and predictability of unique reservoir facies

that occur in association with OAE. Are recovery trends global or do they relate to

palaeoceanographic positions?

• Stratigraphy: Shift in understanding of tectono-eustasy to eco-tectono-eustasy,

especially for Mesozoic carbonate platforms. Is it becoming increasingly

appropriate to move away from the accommodation-control model?

• Predictability/variability: Marked variability exists within OAE systems as well as

between OAE systems. How do we better approach predictability in order to affect

exploration efforts?

Classification: Internal

Livello Bonarelli: 1m

60

m

13 March 20172 Classification: Internal © Statoil ASA

World’s effective SR through time. Klemme and Ulmishek (1991)

Neocomian

3%

Aptian-Turonian

29%

Coniacian-Eocene

3%

Oligo-Miocene

13%

Cambro-Ordovician

1%Silurian

9%U. Devonian-Tournaisian

8%

Penn.-L. Perm

8%

M/U. Permian

1%

Jurassic

25%

Jenkyns, 2010

Importance of considering OAE in exploring hydrocarbon systemsCa. 50% of SR are interpreted as related to known OAE

Source Rock: Stratigraphic association between OAE and major SR intervals

Reservoir: Stratigraphic association between OAE and unique reservoir facies

that may favor eutrophic/heterozoan organisms. These tend to be very grainy

systems.

Stratigraphy: Association between OAE and seismically-resolvable

stratigraphic breaks that can be mapped over hundreds of km2, especially on

Mesozoic carbonate shelves. They can also serve as markers for finer-scale

correlation.


• Bu Hasa Field (Abu Dhabi, UAE): Discovered 1962

− Avg porosity: 5-27%; Avg perm: 0.1-120 mD

− Pay thickness 70-100m

Production:

− Oil (BBL) reserves: 6.52 BBL

− Oil production: 600K bl/day

Example: Reservoir- Cretaceous OAE 1A Recovery, Shuaiba Lithocodium boundstones and grainstones

Rameil et al., 2010

Strohmenger et al., 2006


OAE 1A/B

OAE 2

OAE 1A/B

OAE 2

Example: Packaged play OAE 1A, Mesozoic of N. GoM

Goldhammer (1999)

OAE form seismically-resolvable stratigraphic

breaks that can be mapped over hundreds of

km2. Event recovery reefs with grainstone

aprons are also easily imaged.

Comanche Shelf, Texas

Example: James Production in Houston County to Shelby

county (1983)

Oil (BBL): 172,895,647

Gas (MCF): 32,864,000

James Limestone, OAE 1A recovery


Towards a predictive facies model: OAE 1A/B Northern GoM

• Highlight role of repeated OAE’s in shaping Cretaceous platform in NW

Gulf of Mexico

• Carbonates are very good recorders of environmental change. This allows

us to outline the sequence of events associated with OAE-driven demise

and recovery of carbonate platforms

• Provide examples of OAE-linked stratigraphic signals

• Example of OAE-driven backstepped platforms and intrashelf basins. May

be a characteristic of greenhouse platforms (ex, Devonian, Cretaceous)

• Consider the differential response of the NW GOM platform relative to

eastern Tethys


Gulf of Mexico Paleogeography - Albian

Kerans et al., 201413 March 20178 Classification: Internal © Statoil ASA

?

Purpose: Address unknowns in correlation,

depositional architecture, and stratigraphic

response to environmental forcing to better

affect subsurface predictability

- Conceptual depositional models affect the

way we correlate.

- How we correlate affects how we map

- How we map affects how we make lateral

facies predictions


Sycamore ConglomerateSycamore Ss.

and conglom.Hammett

Shale

Pine Island

Shale


OAE 1A Onlap – Waltherian Considerations


Broader Conclusions• Development of the Cretaceous platform of NW GOM was impacted by the OAE1A,

OAE1B, OAE1D, and OAE2 events. OAE 1A and OAE 2 were major events that

affected platform arcitechture.

• The pre-OAE1A mixed mineralogy flat-topped platform was reduced to a slowly

accumulating calcitic ramp and eventually drowned. This situation repeats at OAE2

• Eco-accommodation-driven OAE cycles operate at a range of scales and are the

main driver of Cretaceous platform architecture in the Western Tethys and GoM.

These events occur regardless of eustatic position. However, not all OAE have the

same affect on platform architecture.

• Demise of benthic carbonate producers and lack of major siliciclastic input may

provde an environment well suited for SR accumulation and preservation.

• OAEs provide a global framework for correlation coupled with biostratigraphic and

chemostratigraphic constraints


What’s new?

• While many Mesozoic stratigraphic intervals are known working hydrocarbon

systems in the subsurface, the link between the those systems and the OAE have

only recently been established. This is especially true for OAE-related reservoir

and OAE-related packaged plays. In other words, many OAE related hydrocarbon

systems were discovered without the realization that they formed as a result of

OAE.

• Predictive stratigraphy around OAE systems- both as source rocks and as reservoir

is a very new topic. We in research should improve our understanding of these

systems, including better understanding both source rock and reservoir variability,

and how to better geochemically recognize fingerprints of specific events.

• Exploration should apply these concepts to any region under evaluation. This is of

particular importance in Mesozoic and/or carbonate systems.

oil&gas thought-leader webinar - new plays for old ideas - dr. rob forkner

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