Estimation and destination of some of the eroded Post Mid-Miocene sediments using a classic method- Vitrinite Reflectance (VR). 28 TH of February, 2013
Feb 24, 2016
Estimation and destination of some of the eroded Post Mid-Miocene
sediments using a classic method- Vitrinite Reflectance (VR).
28TH of February, 2013
2
• 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
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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.
• 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
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
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)
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
• 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