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

Why do this study? Why do this study? What is Vitrinite Reflectance? What is Vitrinite Reflectance? Location of wells Location of wells VR – depth plots VR – depth plots VR – temperature plots VR – temperature plots Summary Summary Why do this study? Why do this study? What is Vitrinite Reflectance? What is Vitrinite Reflectance? Location of wells Location of wells VR – depth plots VR – depth plots VR – temperature plots VR – temperature plots Summary Summary 2 Presentation Outline

3 Why this study? Unconformities. (Higgs. 1997) Convergent margin phase: 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?

Organic Matter Fractionation

Dispersed Vitrinite

8 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 Measurements

Note the lg scale on the x axis Can be used to estimate eroded sediment, Dow (1977) VR vs Depth plots. Moolenaar, m

Dow (1977) The 0.2 estimate has limitations 1) No significant unconformities 2) Heating rate of degrees C/ Myrs (no igneous intrusions 3) No large variations in the geothermal gradient 4) 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

Maximum Palaeotemperature vs VR values 1)Saxony Basin, Germany 2)North Sea 3)Kearl Lake, Alberta 4)Santos Basin, Brasil 5)Mahakam Delta, Indonesia 6)Gulf Of Mexico

14 Well locations Well A Well B Well C Well E Well D

Ro from Well A with an estimated 4552’ to 1300’ of missing sediment. Ro from Well A with an estimated 4552’ to 1300’ of missing sediment. Depth (ft) Cretaceous Oligocene Miocene Early Pliocene Eocene 0.5 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/ 0 C Present day temperatures / 0 C Difference / 0 C 6000Miocene Miocene Oligocene Eocene Cretaceous 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? 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 Cretaceous Missing Mid-Miocene and Late Pliocene- Present sediment 0.5 Depth (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 / 0 C Present day temperatures / 0 C Difference / 0 C 2000 L Miocene to E. Pliocene E. Miocene Oligocene to Palaeocene Cretaceous Cretaceous Average difference in temperatures is 38C

Ro from Well C with an estimated 4970’ to 2689’ of missing sediment?. Ro from Well C with an estimated 4970’ to 2689’ of missing sediment?. Depth (ft) Eocene Early-Miocene 0.5 Oligocene Late Pliocene to Pleistocene Missing Mid to Late Miocene

Depth (ft) Age Estimated Reflectance value Maximum calculated palaeotemperatures /C Present day temperatures /C Difference 2800 E.Miocene E.Miocene Oligocene Oligocene Oligocene/ Eocene Difference between the maximum palaeotemperature and the present day temperature- Well C Average difference in temperatures is 50C

Ro from Well D with an estimated 6000’ of missing sediment. Ro from Well D with an estimated 6000’ of missing sediment. Early Cretaceous Pliocene Pleistocene Y= ln(x)-9148 Depth (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 2350L Pliocene Early Pliocene Early Pliocene Late Miocene E. Cretaceous Early Cretaceous Average Pre Miocene difference in temperatures is 57

23 Well locations Well A Well B Well C Well E Well D

Ro from Well E with an estimated 300’ to 2740’ of extra sediment Ro from Well E with an estimated 300’ to 2740’ of extra sediment Late Pliocene to Early Pleistocene? Late Pliocene Approximately 5,000’ of reworked or recycled vitrinite. Possible MLE equivalent The VR data was backed up with pore maturity data 0.5 Y= (lnx) 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 L Pliocene to E Pleistocene L Pliocene to E Pleistocene Late Pliocene Late Pliocene Late Pliocene Late Pliocene Difference between the maximum palaeotemperature and the present day temperature- Well E Average Late Pliocene difference in temperatures is 1

Trinidad and Tobago AssetDD Month YearPage 26 Columbus Basin Upper Tertiary Depocenter Caroni Basin Upper Tertiary Depocenter Non Deposition/Erosion Eastern Offshore Ties? Cruse-Forest- Morne L’Enfer Depocenter Gros Morne- Mayora Depocenter Late Tertiary Summary Plio-Pleistocene tectonics

Top Cretaceous, Gibson et al Onshore Cretaceous is at 4000’ to 6000’. Pleistocene Southern Range transpressional uplift at about 1.6 Ma – regional Southern Anticline Inversion of Caroni Basin

28 Where is the reworked sediment coming from? Well A Well B Well C Well E Well 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 AssetDD Month YearPage 36 Structural Domains, Trinidad and Tobago