Estimation and destination of some of the eroded Post Mid-Miocene

sediments using a classic method- Vitrinite Reflectance (VR).

28TH of February, 2013

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• Why do this study?• What is Vitrinite Reflectance?• Location of wells• VR – depth plots • VR – temperature plots• Summary

Presentation Outline

3

Why this study? Unconformities. (Higgs. 1997)

Convergent marginphase: encroachment

of Caribbean plate

Passive margin phase

• Where is the missing sediment and can it be potential reservoirs?

MACERAL (from Latin: “macerare”, to soften) Stopes, 1935

• “Macerals are constituents of coals,

occurring naturally in the sedimentary, metamorphic, and igneous materials of the earth ”

Spackman, (1958)

What is a Maceral?

5

What is Vitrinite?

SOURCE MACERALMACERAL

GROUPKEROGEN

TYPE

DEGRADED ALGAE & BACTERIA SAPROPEL

ALGAE ALGINITE

RESINITE LIPTINITECUTINITE TYPE II

SPORINITEHIGHERPLANTS COLLINITE

TELINITE

FUSINITESEMI-FUSINITE

FUNGI SCLEROTINITE

TYPE I

VITRINITE TYPE III

INERTINITE TYPE IV

Dispersed Vitrinite

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What is Vitrinite Reflectance- VR

•Vitrinite Reflectance (%Ro) is a measurement of the percentage of light reflected off the vitrinite maceral at oil immersion

• Vitrinite reflectance Ro as a thermal indicator

• Thermodynamic record are preserved in rock and such records are irreversible.

• Increase in burial causes progressive increase in temperature; thus maturity increases with depth.

Dispersed Vitrinite Ro Histograms should be based on 40-100 Measurements

• Note the lg scale on the x axis

• Can be used to estimate eroded sediment , Dow (1977)

VR vs Depth plots . Moolenaar , 1996

1400 m

Dow (1977)

The 0.2 estimate has limitations1) No significant unconformities 2) Heating rate of 1- 10 degrees C/ Myrs (no igneous

intrusions3) No large variations in the geothermal gradient4) Depends on whether or not the studied section is in

Tropical or Temperate climate.5) Indicates the depth of diagenesis

Erosion estimation based on Dow (1977) ; using 0.2 as a near surface VR estimate

• VRo valued tied to a maximum palaeo-temperature

• Indicates the oil window for Type 1 and Type 2 kerogens

VR values used in thermal history reconstruction

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3 3.4 3.5 3.60

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

f(x) = 91.9607060614558 ln(x) + 154.181040040161R² = 0.884039339484359

Maximum Palaeotemperature vs VR values

1) Saxony Basin, Germany2) North Sea3) Kearl Lake, Alberta4) Santos Basin, Brasil5) Mahakam Delta,

Indonesia6) Gulf Of Mexico

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Well locations

Well AWell B

Well C Well EWell D

Ro from Well A with an estimated 4552’ to 1300’ of missing sediment.

Dept

h (ft

)

Cretaceous

Oligocene

Miocene

Early Pliocene

Eocene

0.50.1 1

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0

f(x) = − 14576.1176220496 ln(x) − 18906.9471275173

Missing Late Pliocene to E.

Pleistocene, Early Miocene and Palaeocene

L. Cretaceous source rock is in the

main oil window

Depth (ft) Age Estimated Reflectance value

Maximum calculated palaeotemperatures/ 0C

Present day temperatures/0C

Difference / 0 C

6000 Miocene 0.41 72 51 218000 Miocene 0.48 87 65 2210000 Oligocene 0.55 99 79 2012000 Eocene 0.62 112 94 1814000 Cretaceous 0.71 123 100 23

Difference between the maximum palaeotemperature and the present day temperature- Well A

Average difference in temperatures is 21C

Ro from Well B with an estimated 5851’ to 2956’ of missing sediment?

Cretaceous

Late Miocene to Early Pliocene

Early Miocene to Oligocene

Oligocene to CretaceousMissing Mid-Miocene

and Late Pliocene-Present sediment

0.50.1 1

-12000

-10000

-8000

-6000

-4000

-2000

0

f(x) = − 12975.0233763784 ln(x) − 15031.3156857789

Dept

h (ft

)

Missing Late Pliocene to E. Pleistocene, Early

Miocene

L. Cretaceous source rock is in the

main oil window

Difference between the maximum palaeotemperature and the present day temperature- Well B

Depth (ft) Age Estimated Reflectance value

Maximum calculated palaeotemperatures/ 0C

Present day temperatures/ 0C

Difference / 0 C

2000 L Miocene to E. Pliocene

0.36 60 22 38

3000 E. Miocene 0.39 68 29 394000 Oligocene to

Palaeocene0.41 72 36 36

5400 Cretaceous 0.47 85 46 397000 Cretaceous 0.52 94 58 36

Average difference in temperatures is 38C

Ro from Well C with an estimated 4970’ to 2689’ of missing sediment?.

Dept

h (ft

)

Eocene

Early-Miocene

0.5

Oligocene

Late Pliocene to Pleistocene 0.1 1

-5500

-5000

-4500

-4000

-3500

-3000

-2500

-2000

f(x) = − 10220.9354349807 ln(x) − 11480.2678809097

Axis Title

Axis Title Missing Mid to Late Miocene

Depth (ft)

Age Estimated Reflectance value

Maximum calculated palaeotemperatures/C

Present day temperatures/C

Difference

2800 E.Miocene 0.41 72 27 45

3500 E.Miocene 0.47 85 33 524000 Oligocene 0.49 89 36 534500 Oligocene 0.5 91 40 51

5000 Oligocene/ Eocene

0.51 92 43 49

Difference between the maximum palaeotemperature and the present day temperature- Well C

Average difference in temperatures is 50C

0.1 1

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0

Axis Title

Axis Title

Ro from Well D with an estimated 6000’ of missing sediment.

Early Cretaceous

Pliocene

Pleistocene

Y= -10854ln(x)-9148

Dept

h (ft

)

Late Miocene

Missing the Late

Cretaceous to Mid Miocene

0.5

Any possible L. Cretaceous source rock maybe in the

oil to gas phase

Difference between the maximum palaeotemperature and the present day temperature- Well D

Depth (ft) Age Estimated Reflectance value

Maximum calculated palaeotemperatures/ C

Present day temperatures

Difference

2350 L Pliocene 0.3 43 40 3

5750 Early Pliocene 0.4 70 68 2

7240 Early Pliocene 0.45 81 80 1

9300 Late Miocene 0.55 99 98 19800 E. Cretaceous 1.05 159 102 5712200 Early

Cretaceous1.3 178 121 57

Average Pre Miocene difference in temperatures is 57

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Well locations

Well AWell B

Well C Well EWell D

0.1 1

-18000

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0 R0 (%) from well E

Dept

h td

v/ss

(ft)

Ro from Well E with an estimated 300’ to 2740’ of extra sediment

Late

Plio

cene

to

Early

Ple

istoc

ene?

Late

Plio

cene

Approximately 5,000’ of reworked or

recycled vitrinite. Possible MLE

equivalent

The VR data was backed up with pore

maturity data

0.5

Y= -13881(lnx)-24272

Sediment reached approximately 92 C

Uplift has to be quick in E.Pleistocene

Vitrinite in deep water

Depth (ft) Age Estimated Reflectance value

Maximum expected palaeotemperatures

Present day temperatures/C

Difference

4325 L Pliocene to E Pleistocene

0.29 40 29 11

6305 L Pliocene to E Pleistocene

0.54 98 40 58

8315 L Pliocene to E Pleistocene

0.39 68 52 16

10315 Late Pliocene 0.37 63 63 012305 Late Pliocene 0.41 72 73 -114320 Late Pliocene 0.48 87 87 015567 Late Pliocene 0.52 94 93 1

Difference between the maximum palaeotemperature and the present day temperature- Well E

Average Late Pliocene difference in temperatures is 1

Top Cretaceous , Gibson et al. 2005

Onshore Cretaceous is at 4000’ to 6000’.

  Pleistocene• Southern Range transpressional uplift at about 1.6 Ma – regional Southern Anticline•Inversion of Caroni Basin

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Where is the reworked sediment coming from?

Well AWell B

Well C Well EWell D

Seismic indicates a strong NE-SW bias

• Irreversible • Insensitive to rock composition • Covers wide temperature range • Present in most sedimentary rocks (Silurian

to present)

Advantages of Vitrinite Reflectance (Ro)

Issues with VRo: Sample Preparation Affects Vitrinite Reflectance Values

Effect on Ro

• Caving Lower • Rough vitrinite Lower • Suppression Lower • Mud contamination Usually Lower • Oxidized vitrinite Usually Higher • Recycled/reworked Higher • Incorrect maceral identification Both • Statistical errors (few measurements) Both

Vitrinite Reflectance of Ditch Cuttings Has Pitfalls

So what have we learned?

• Vitrinite is a coal maceral derived from wood. • Vitrinite reflectance cannot tell you whether or not a rock • generated oil or gas• It may be difficult to accurately estimate the amount of missing

sediment due to differences in thermal gradients and thermal conductivities of the sediment.

• The deep water area has some definitive reworked sediment (the origin and final site of deposition is difficult to determine) Are there potential MLE equivalent reservoirs in the deep water?

• There exists different maturities for sediment of the same age onshore Trinidad.

• Can reworked sediment be reservoirs for the deep water area?

Summary

Trinidad and Tobago Asset DD Month Year Page 36

COLUMBUS BASIN

NORTHERN RANGE

Inner Fold a nd Thrust Be lt

Diapiric Belt

Structural Domains , Trinidad and Tobago