how many source rocks do I have? 1 Samuel Rivas, J. Grimmer, A. - - PowerPoint PPT Presentation

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how many source rocks do I have? 1 Samuel Rivas, J. Grimmer, A. - - PowerPoint PPT Presentation

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Basin modeling at the Songkhla Basin (Gulf of Thailand) or: how many source rocks do I have? 1 Samuel Rivas, J. Grimmer, A. Alaminos, J. Navarro. Cepsa E.P., S.A. April, 5 th . 2016 Outline Conclusions, first! Introduction (from

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Basin modeling at the Songkhla Basin (Gulf of Thailand) or: how many source rocks do I have?

Samuel Rivas, J. Grimmer, A. Alaminos, J. Navarro. Cepsa E.P., S.A. April, 5th. 2016

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Outline

  • Conclusions, first!
  • Introduction (from a regional to local perspective)
  • Source rocks of the Songkhla Basin (which and what are they?)
  • Basin modeling (featuring 1Ds, vitrinite reflectance suppression, and 3D

models)

  • Conclusions, again!
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Conclusions, first!

  • The Lower Oligocene shales are the main source rock in Songkhla. Lower Miocene

shows, with the available data, much less potential.

  • These are oil-prone lacustrine shales with contributions of terrestrial organic material,

and have a fair-to-good quality (1-5%TOC).

  • Vitrinite reflectance (Ro%) suppression is occurring in the basin; which means Ro% is

not a good proxy for maturity.

  • Lower Oligocene entered the oil window as early as the Late Oligocene (23 Ma), coeval

with expulsion onset, which peaked in the Mid-Late Miocene (12-5 Ma).

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Thailand

Introduction: Location

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Introduction: Regional geological history

  • 1. Amalgamation of crustal blocks from Devonian to Eocene times.

Metcalfe, 2011. Modified from Metcalfe, 2011.

W E

2 2 1 3 3

Modified from Doust and Sumner, 2007.

EARLY EOCENE

1

Tectonic elements map

  • f South East Asia, at

present day You are here

W E

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Introduction: Regional geological history

  • 2. After the Himalayan collision, rift basins formed and filled from the Eocene to present-day.

Modified from Polachan and Sattayarak, 1991. Rifting is younger northward!

Pre-Tertiary crust All the pre-Tertiary crust is extended, and filled with sedimentary basins

N N

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Introduction: the Songkhla Basin

SW NE

Top Lower Miocene Top Upper Oligocene Top Lower Oligocene Top Mid. Miocene Top Eocene Top Basement

2.5km

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Source rocks of the Songkhla Basin

Lower Oligocene – The proven source rock for the Songkhla Basin Lower Miocene? – A proven source rock in other Gulf of Thailand basins

What are the evidences?

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Source rocks of the Songkhla Basin: Lower Oligocene

Lower Oligocene: lacustrine shales with occasional lacustrine turbiditic events. Depositional environment can be fit into the tectonic setting of the basin at the moment. 10065’ 10066’

TOC=1-5%

A A ’

Modified from Keighley, 2008.

Top Lower Oligocene

A A’ A A’

Modified from Keighley, 2008. SW NE

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Source rocks of the Songkhla Basin: Lower Miocene

Grey (silty) to red claystones with signs of subareal exposure (siderite nodules, roots..), which correspond to flood plains. 4253’ 4254’

Not very promising : ( ….

Flood plain 2 km

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Source rocks of the Songkhla Basin: TOC and HI

TOCs from 11 wells: 85% of the values belong to the Oligocene and below. Organic richness is in the Lower Oligocene and below! TOCMax=5.26% HIs and OIs from 9 wells, all from Lower Oligocene: mixed Type I-III signature. Palynology, paleogeography, and more geochemistry support this HI=100-900 mgHC/g OC

100 200 300 400 500 600 700 800 900 1000 20 40 60 80 100 120 140 160 180 200

HI (mg HC/g Organic Carbon OI (mg CO2/g Organic Carbon)

3000 4000 5000 6000 7000 8000 9000 10000 11000 1 2 3 4 5 6 7

Depth (ft) TOC (%)

Above Lower Oligocene Lower Oligocene Below Lower Oligocene

Lower Miocene

Type I Type III Lower Oligocene

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Source rocks of the Songkhla Basin: isotopes and biomarkers

  • 10
  • 9
  • 8
  • 7
  • 6
  • 5
  • 4
  • 3
  • 2
  • 1

1 2 3 4 5 6 7

2 4 6 8 10

Canonical Variable (CV) Pristane/Phytane

Fluvio-deltaic Marine Lacustrine

Calculated from δ13C of aromatic and saturate HCs and used to distinguish terrigenous from marine sources (Sofer, 1984).

Oil samples ( ) and rock extract ( ) analyses from 7

  • wells. Confirmation of the lacustrine source!

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1

H31R/Hopane C26/C25 tricyclic terpanes

Lacustrine Marine shales Marls Carbonates

Oil sample analyses from 5 wells. Guess what? More lacustrine source!

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Source rocks of the Songkhla Basin: quality

100 200 300 400 500 600 700 800 900 1000 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00

HI(mg HC/g TOC) TOC (%)

Good Lower Oligocene source rock values show a fair-to-good source rock! Lower Miocene…insufficient data for a meaningful answer, but probably a poor source rock Poor Fair Very good

Modified from Tommeras and Mann, 2008.

Lower Oligocene

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Source rocks of the Songkhla Basin: mature?

…there is a whole basin producing some oil, so definitely YES they are mature!!! We need to have a better understanding than that!

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Basin modeling: there is something wrong with these %Ro…

T calibrated models show a mature Lower Oligocene source rock %Ro calibrated models show a very immature Lower Oligocene source rock !!!

How can that be?!

Well-1 Well-2 Well-3

Temperature data Vitrinite ref. data

Immature Mature

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Basin modeling: there is something wrong these %Ro…

Calculating an empirical vitrinite reflectance from Tmax (Jarvie, 2005) shows much higher %Ro values than the observed. Below, an example from the deepest Songkhla well.

Measured vitrinite reflectance Equivalent vitrinite reflectance from Tmax

Vitrinite reflectance suppression!

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Basin modeling: there is something wrong these %Ro…

Perhydrous vitrinites are causing vitrinite reflectance suppression at the Songkhla Basin; %Ro values are lower that what they should be. This happens in other basins around the world (Petersen, 2009, Waples, 1994), specially in tropical areas.

H2O

This makes plant material (vitrinite) less reactive to heating, thus giving lower maturities

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Basin modeling: input and calibration

Knowing we can only trust fully the temperature data to calibrate the models… we jump to the 3D model!.

11 Layers 12 Horizons 1 Type I source rock, TOC=2%, HI=900mgHC/gOC

(no reason for a second source rock)

McKenzie rift 34-10Ma

Calibration examples (with temperature data) Input

A A’ A A’

Temperature data

N

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Basin modeling: results

Source rock maturity

  • L. Oligocene enter the
  • il window at 24 Ma
  • L. Oligocene Generated Mass/Ma

Max generation occurs in Mid-Late Miocene

  • L. Oligocene Transformation Ratio

TR increases progressively

1D burial plots at the Lower Oligocene depocentre

  • L. Miocene enter the oil

window at 8 Ma

Lower Oligocene present day maturity map Depocentre

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Basin modeling: results

Expulsion initiation 23.0 Ma Expulsion peak 11.6-5.0 Ma Expulsion from source rock layer (events) Expulsion from source rock layer (cumulative) 2.7 Billion barrels

Expulsion begins in Late Oligocene and peaks in Mid-Late Miocene.

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Conclusions, again!

  • The Lower Oligocene shales are the main source rock in Songkhla. Lower Miocene shows, with

the available data, much less potential.

  • These are oil-prone lacustrine shales with contributions of terrestrial organic material, and have a

fair-to-good quality (1-5%TOC).

  • Vitrinite reflectance (Ro%) suppression is occurring in the basin; which means Ro% is not a good

proxy for maturity.

  • Lower Oligocene entered the oil window as early as the Late Oligocene (23 Ma), coeval with

expulsion onset, which peaked in the Mid-Late Miocene (12-5 Ma).

The summary of our knowledge on the source rocks and maturity of the basin!

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References

  • Doust, H., and Sumner, H. S. [2007] Petroleum systems in rift basins: A collective approach in Southeast Asian

basins: Petroleum Geoscience, v. 13, p. 127–144.

  • Jarvie, D.M., Hill, R.J., Pollastro, R.M. [2005] Assessment of the Gas Potential and Yields from Shales: the Barnett

Shale Model in Cardott, B.J. (ed.), Unconventional energy resources in the southern Midcontinent, 2004 symposium: Oklahoma Geological Survey Circular 110, 2005, p. 37-50.

  • Keighley, D. [2008] A lacustrine shoreface succession in the Albert Formation, Moncton Basin, New Brunswick:

Bulletin of Canadian Petroleum Geology, v. 56, p.235-258.

  • Metcalfe, I. [2011] Palaeozoic–Mesozoic history of SE Asia: Geological Society Special Publication, v. 355, p. 7–35.
  • Petersen, H. I., Sherwood, N., Mathiesen, A., Fyhn, M. B. W., Dau, N. T., Russell, N., Bojesen, J. A., Nielsen, L. H.

[2009] Application of integrated vitrinite reflectance and FAMM analyses for thermal maturity assessment of the northeastern Malay Basin, offshore Vietnam: Implications for petroleum prospectivity evaluation. Marine and Petroleum Geology 26, 319-332.

  • Sofer, Z. [1984] Stable carbon isotope compositions of crude oils: application to source depositional environments

and petroleum alteration. AAPG Bulletin, 68, 31-49.

  • Waples, D. W. [1994] Maturity Modeling: Thermal Indicators, Hydrocarbon Generation, and Oil Cracking: Chapter

17: Part IV. Identification and Characterization. AAPG Memoir 60: The Petroleum System--From Source to Trap, 285-306.

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Thanks for attending!

Questions? Enjoy the event and see you next time!

And feel free to contact! samuel.rivasd@cepsa.com