This multiclient study examines geological data and high-resolution geochemical parameters of three petroleum systems found in the Espírito Santo Basin: the pre salt Neocomian/Barremian lacustrine system, the post salt Albian/Turonian marine anoxic system and the Tertiary marine deltaic system that are not always active in the same areas of the basin. In addition to characterizing the various source rock facies, it illustrates how variable are the thermal maturity stages and alteration processes that occur in shallow platform reservoirs.

This study provides to petroleum analysts of E&P companies a good compilation of detailed maps and geochemical data of the entire basin.

Full references of all images are listed in the reports

1. Introduction
2. Regional geology and tectonic framework
3. Exploratory history
4. Elements of the petroleum systems
   1. Source rocks and hydrocarbons
   2. Reservoirs, seals and traps
      1. Mariricu fm. (mucuri mb.)
      2. Regência / são mateus
      3. Urucutuca
5. Processes of the petroleum systems (generation, migration and accumulation)
6. Petroleum systems of the espirito santo basin
   1. Mariricu fm. (mucuri mb.)
   2. Regência / são mateus
   3. Urucutuca
7. Exploratory implications and risks
8. 2D Basin Modeling in the Espirito Santo Basin (Line ESS-1)
   1. Geological characteristics of the cross section
   2. Source rock characteristics
   3. Maturity analysis
   4. Migration analysis
   5. Analysis of the fluid system
   6. Biodegradation risk
   7. Conclusions
9. 2D Basin Modeling in the Espirito Santo Basin (Line ESS-2)
   1. Geological characteristics of the cross section
   2. Source rock characteristics
   3. Maturity analysis
   4. Migration analysis
   5. Analysis of the fluid system
   6. Biodegradation risk
   7. Conclusions
10. Conclusion

1. Location map of the Potiguar Basin with its boundaries, limited to west by the Fortaleza High, which separates it from the Ceará Basin, to the east by the Touros High, and to the south by the basement outcrops. A-A’ cross-section is shown in Figure 2. Simplified tectonic framework and main petroleum accumulations of the Potiguar Basin is also shown here (modified from Bertani et al., 1990).
2. Schematic cross-section in the Potiguar Basin (see location in the map bellow) (modified from Bertani et al., 1990).
3. Stratigraphic chart of the Potiguar Basin (modified from Araripe & Feijó, 1994).
4. Location map of the selected Oil Samples used in the study.
5. Location map of the selected Rock Eval data and 2D modeled line used in the study.
6. Location map of the geochemical logs shown below (based on Neves, 1989).
7. Geochemical log of the onshore WELL 1-RC-2-RN showing the source rocks of the Pendência Formation in the Potiguar Basin. Note the complete transformation and expulsion of hydrocarbons below 1250m.
8. Geochemical log of well 1-RNS-15-RN, Potiguar Basin. Note the presence of organic-rich sediments from Alagamar and Pendência Formations in the same well
9. Van Krevelen type diagram of the Pendência Formation source rocks located in onshore areas (Trindade el al., 1992).
10. Natural Series for the selected rock-eval data of the Pendência Formation.
11. Thickness of Pendência source unit with TOC > 1%.
12. Highest values TOC values for the Pendência formation samples.
13. Map of the S2 values for the Pendencia formation samples.
14. Map of the TMAX values for the Pendencia formation samples.
15. Location of the geochemical log shown in Figures 15 and 16 with the main geochemical values for the marine hypersaline sequence.
16. Geochemical log of well 1-RNS-5 (see location in figure 14) showing the Alagamar Fm source rocks (Camadas Ponta do Tubarão Member, CPT) together with sediments of Pendência Formation (after Trindade el al., 1992).
17. A geochemical log of 7-MA-11 well showing the organic-rich sediments of Camadas Ponta do Tubarão Member of the Alagamar Formation. Observe the distribution of the organic-rich layers intercalated with organic-poor sandstones do Tubarão and Upanema sequences.
18. A geochemical log of 1-CES-121 well showing the organic-rich sediments of Alagamar Formation composed of CPT and Upanema Members. Observe the distinction between the Camadas Ponta do Tubarão (upper part) and Upanema organic-rich sediments (lower part).
19. Van Krevelen type diagram of the Alagamar Formation source rocks (Trindade el al., 1992).
20. Natural Series for the selected rock-eval data of the Alagamar Formation.
21. Map of the thickness values for the Alagamar source units.
22. Map of the TOC values for the Alagamar formation samples
23. Map of the S2 values for the Alagamar formation samples
24. Map of the TMAX values for the Alagamar formation samples
25. Spatial distribution of the Pods of Generation of the Potiguar Basin based in the location of all the oils discovered up to now.. Note that the most of the hydrocarbon occurrences are composed of mixed oils, suggesting therefore an overlay of lacustrine and marine migration pathways.
26. Location Map of the oils from Potiguar Basin analyzed in this study.
27. Oils type versus reservoir depth, name and age in the Potiguar Basin
28. Map showing a summary of the petroleum system of the Potiguar Basin. Observe the occurrence and juxtaposition of the marine and lacustrine petroleum systems towards deep water in the basin. Also, the presence of regional NE-SW fault systems is a very important feature controlling the migration pathways in the whole Basin. Such feature suggests that the presence of the active pods of generation are located deep offshore.
29. API gravity versus Depth (m) of the oils from the Potiguar oils. Note that, as a general trend, the API gravity data of the do suggest a depth control for oil quality. The oils considered outsider from this trend are mixed oils composed of contribution from the marine and lacustrine petroleum Systems.
30. API versus Saturates content of the Potiguar oils. Note that oil mixtures and biodegradation do affect the bulk data and does not allow good differentiation among the oil types from the Potiguar Basin. Except the mixed oils, Higher the saturate content higher the API gravity of the oils.
31. API versus Sulfur content of the Potiguar oils. Note that oil mixtures and biodegradation do affect the sulfur data and does not allow good differentiation among the oil types from the Potiguar Basin. Except the mixed oils, Higher the sulfur content lower the API gravity of the oils. Also, lacustrine oil source do affect sulfur data lowering their values.
32. Map displaying the API gravity data of the oils analyzed in this study. Note the increase of API data close to the deep offshore pods. By contrast, the onshore oils showed the lower values (biodegraded or long distance from the pods)
33. Map displaying the sulfur data for the oils analyzed. Note a good correlation with the API degree map from figure 26.
34. Carbon isotope of saturates versus Pr/Phy indices from the oils analyzed for the Potiguar Basin. Note that the lacustrine oils, as reported by Mello, 1988, present very low values of carbon isotopes when compared with the marine ones. Also, the always present very high Pristane over Phytane ratio (>> 1.5%).
35. Gas chromatograms of the oil types of the Potiguar Basin. Note that biodegradation, thermal evolution and oil mixing can alter y the GC profile. The presence of high molecular weight compounds in the oils suggests higher plant input and oil mixing.
36. M/Z 191 Fragmentograms of oils from Potiguar Basin. Note the high abundance of gammacerane in the hypersaline and lacustrine brackish compared with the lacustrine fresh water and marine anoxic oils. See also their carbon and sulfur data.
37. M/Z 217 Fragmentograms of oils from Potiguar Basin. Note the high abundance of 4-methyl steranes in the lacustrine oils when compared with the marine ones. Also note the carbon distributions regarding C27 against C29 steranes.
38. M/Z 259 Fragmentograms of oils from Potiguar basin showing the high relative abundance of lacustrine marker TPP polyprenoids over the C27 diasteranes, in the lacustrine oils. In the marine ones the TPP compounds are lower than the C27 diasteranes.
39. M/Z 231 Fragmentograms of oils from Potiguar basin. Note the differences in the abundance of C29 and 3methyl/ 4methyl triaromatic steranes between the lacustrine and marine oils. The lacustrine oils present higher concentrations of C29 and 4methyl triaromatic steranes.
40. M/Z 245 Fragmentograms of oils from Potiguar Basin. The marine hypersaline oil from the CPT Member show higher abundances of C29 4methyl triaromatic steranes than the oil from the Galinhos Member (marine anoxic).
41. Mass chromatograms from metastable ion monitoring of C27 to C30 steranes compounds of a Pendência oil from Potiguar Basin. Note the absence of C30 steranes in the lacustrine oil.
42. Mass chromatograms from metastable ion monitoring of C27 to C30 steranes compounds of a lacustrine oil sourced by Upanema source rocks from Potiguar basin. Note the absence of C30 steranes in the lacustrine oil.
43. Mass chromatograms from metastable ion monitoring of C27 to C30 steranes compounds of a lacustrine oil sourced by CPT source rocks from Potiguar Basin. Note the presence, although in low amounts of C30 steranes in this marine hypersaline oil.
44. Mass chromatograms from metastable ion monitoring of C27 to C30 steranes compounds of a lacustrine oil sourced by Galinhos source rocks from Potiguar Basin. Note the presence, although in low amounts of C30 steranes in this marine carbonate oil.
45. Gas chromatograms of the lacustrine oil types of the Potiguar Basin. Note the high molecular weight compounds in the lacustrine oils.
46. M/Z 191 Fragmentograms of lacustrine oils from Potiguar basin. Note the high abundance of gammacerane in the lacustrine brackish compared with the lacustrine fresh water.
47. M/Z 217 Fragmentograms of Lacustrine oils from Potiguar basin. Note the high abundance of 4-methyl steranes in the lacustrine oils.
48. M/Z 259 Fragmentograms of lacustrine oils from Potiguar Basin showing the high relative abundance of lacustrine biomarker TPP polyprenoids over the C27 diasteranes.
49. M/Z 231 Fragmentograms of lacustrine oils from Potiguar Basin. Note the differences in the abundance of C29 and 3mthyl/ 4methyl triaromatic steranes between the lacustrine and marine oils. The lacustrine oils present higher concentrations of C29 and 4methyl triaromatic steranes.
50. M/Z 245 Fragmentograms of lacustrine oils from Potiguar basin. The lacustrine oils show lower abundances of C29 4methyl triaromatic steranes.
51. Mass chromatograms from metastable ion monitoring of C27 to C30 steranes compounds of a Pendência oil from Potiguar Basin. Note the absence of C30 steranes
52. Mass chromatograms from metastable ion monitoring of C27 to C30 steranes compounds of an Upanema oil from Potiguar Basin. Note the absence of C30 steranes
53. Gas chromatograms of the marine hypersaline and marine carbonate oil types (Galinhos and CPT Members) of the Potiguar Basin. Note the high molecular weight compounds in the marine oils.
54. M/Z 191 Fragmentograms of marine hypersaline oil types (CPT and Galinhos Mb.) from Potiguar Basin. Note the high abundance of gammacerane compared to the marine carbonate sample.
55. M/Z 217 Fragmentograms of marine hypersaline oil type (CPT) from Potiguar Basin. Note the low abundance of 4-methyl steranes compared to the lacustrine oils shown above.
56. M/Z 259 Fragmentograms marine hypersaline oil type (CPT) from Potiguar Basin showing the low relative abundance of lacustrine biomarker TPP polyprenoids over the C27 diasteranes. The opposite relation occurs for the marine carbonate sample of the Alagamar Fm/Galinhos Mb. of well 3-RNS-137
57. M/Z 231 Fragmentograms of marine hypersaline oil type (CPT and Galinhos members) from Potiguar Basin. Note the differences in the abundance of C29 and 3mthyl/ 4methyl triaromatic steranes between the lacustrine and marine oils. The marine oils present lower concentrations of C29 and 4methyl triaromatic steranes.
58. M/Z 245 Fragmentograms of marine hypersaline oil type (CPT and Galinhos members) from Potiguar Basin. The marine oils show higher abundances of C29 4methyl triaromatic steranes.
59. Mass chromatograms from metastable ion monitoring of C27 to C30 steranes compounds of a marine hypersaline oil type (CPT) from Potiguar Basin. Note the presence, although in low abundances of C30 steranes
60. Mass chromatograms from metastable ion monitoring of C27 to C30 steranes compounds of a Galinhos oil from Potiguar Basin. Note the presence of C30 steranes
61. Plots of Hopane/ Sterane versus Pristane/ Phytane ratios from the oils analyzed for the Potiguar basin. Note that the lacustrine oils, as reported by Mello, 1988, present the highest ratios when compared with the marine ones that agglutinated themselves showing similar values. It is also important to mention the difficulties in differentiating the Aptian marine hypersaline from the Albian-Cenomanian marine anoxic oil types.
62. Gammacerane index versus C34/C35 hopanes from the oils analyzed for the Potiguar Basin. Note that the lacustrine oils, as reported by Mello, 1988, present low ratios when compared with the marine oils. It is also important to mention the good separation among all oil types
63. Plot of diasteranes/ TPP versus 3Me/ 4Me triaromatics from the oils analyzed for the Potiguar basin. Note that the Aptian marine hypersaline/ carbonate oils, as reported by Mello, 1988, present the highest ratios when compared with the oil types. Also, note that the mixed oils presented intermediate ratios.
64. Plot of Gammacerane index versus diasteranes/TPP from the oils analyzed for the Potiguar basin. Note that the Aptian marine hypersaline oils, as reported by Mello, 1988, present the highest gammacerane index when compared with the other oil types. Also, note that the mixed oils presented intermediate ratios.
65. Plot of C29 αββ/(αββ + ααα) versus S/ S+R steranes from the oils analyzed for the Potiguar Basin. Note that there is a good correlation between the increases of the thermal evolution of the oils and the deeper source rocks.
66. Plot of C29 αββ/(αββ + ααα) steranes versus Ts/ Ts+Tm from the oils analyzed for the Potiguar Basin.
67. Map of C29 αββ/(αββ + ααα) steranes from the oils analyzed for the Potiguar basin. Note that there is a good correlation between the increases of the thermal evolution of the oils towards and close to the deep offshore Lows, where the active pods of generation are located. As can be noted the oils close to the coast and more distant from the pods present the lowest thermal evolution data.
68. Map of TS/TS+TM from the oils analyzed for the Potiguar basin. . Note that there is a good correlation between this map with the steranes maturity one. Both showed the increases of the thermal evolution of the oils towards the deep offshore Lows, where the active pods of generation are located.
69. Plot of saturate contents versus Ro equivalent from the oils analyzed for the Potiguar Basin. Note that there is a reasonable correlation between them.
70. Map of Ro Equivalent from the oils analyzed for the Potiguar basin. As can be noted, there is an increases of the thermal evolution of the oils towards and close to the deep offshore Lows, where the active pods of generation are located. Therefore, suggesting a long distance migration pathway from Northern pods towards near shore and onshore areas of the Basin.
71. Map of Nor25H/30H from the oils analyzed for the Potiguar basin. The presence of past biodegraded events coincident with the most mature oils suggested oil mixing from several migration pulse from distinct petroleum system contributing for the same oil accumulation.
72. Diamondoids versus Stigmastanes data of condensates and oils from Potiguar Basin. As can be noted, there are a number of oils that are mixtures non cracked and cracked oils derived from distinct Petroleum Systems occurring together.
73. Schematic cross sections along the Serraria and Pescada/RNS-33 fields showing the entrapment mechanism within the Pendência Formation reservoirs, Potiguar Basin (after Bertani el al., 1990).
74. Petroleum system event chart of the Pendência Source rocks showing the elements and processes that controlled the habitat of Petroleum, in the Potiguar Basin, during the Lowermost Cretaceous time.
75. Schematic cross sections along the Fazenda Belém and Ubarana fields showing the entrapment mechanism of petroleum accumulations in the reservoirs of the Açu and Alagamar formations, Potiguar Basin (after Bertani el al., 1990).
76. Petroleum system event chart of the Alagamar Formation showing the elements and processes that controlled the habitat of Petroleum, in the Potiguar Basin, during the Uppermost Lower Cretaceous time.
77. Location of the regional cross section used for the petroleum systems modeling in this study.
78. Composite seismic line that was used as a basis for the 2D modeling
79. Regional cross section derived from the interpretation of the seismic lines showed on the last figure.
80. Location of the Pescada-Arabaiana and the Pescada Fault Zone.
81. Source rock distribution along the modeled section. Observe the absence of the Alagamar Formation source rocks in the deeper potion of this section.
82. Source rock parameters of the Potiguar basin used in the simulation
83. Present-day temperature distribution along the section after final calibration. The isotherms show a parallel trend regarding the seafloor and basement morphology
84. Vitrinite reflectance distribution along the section after final calibration. The contours show the Shallow Platform Domain as immature and the Deep Platform, Slope and Deep basin gradually in the oil and gas windows.
85. Location of well 1-RNS-22 in the shallow platform domain and its geohistory diagram with thermal calculation. Observe that the Pendência Formation doesn’t occur in this domain
86. Temperature and Vitrinite Reflectance calibration of well 1-RNS-22 using regional data
87. Figure illustrating the low level of transformation ratio of the organic matter belonging to the Alagamar/Galinhos source rock (5%) in the shallow platform portion of the basin.
88. Vitrinite Reflectance profile of the section showing the position of well 3-RNS-86.
89. Geohistory diagram with thermal evolution in well 3-RNS-86. The Pendência source rocks are presently in oil peak generation stage in this well, and the Alagamar Formation is in the oil window.
90. Temperature and Vitrinite Reflectance calibration of well 3-RNS-86 using regional data.
91. Diagram illustrating the medium level of transformation ratio of the organic matter (44%) belonging to the Pendência source rock in the deep platform domain.
92. Diagram illustrating the medium level of transformation ratio of the organic matter (26%) belonging to the Alagamar source rock in the deep platform domain.
93. Diagram illustrating the medium level of transformation ratio of the organic matter (62%) belonging to the Alagamar source rock in the Slope platform domain. Observe the rapid change in slope of the curve at 16 Ma.
94. Transformation ratio (TR) through time at the Slope Domain for the Pendência source rock unit. It is noticeable the fast increase in the transformation ratio at about 16 Million years.
95. High level of transformation ratio of the organic matter of the Pendência source rock unit at the Deep Basin Domain. It is noticeable the fast increase in the transformation ratio at about 16 Million years.
96. Lateral migration along the Alagamar Formation is observed in the model and played a major role conducting petroleum generated at deep pods to shallower levels.
97. Differential compaction between these two domains forces fluids to migrate upwards through the fault zone. This process suggests that these fault zones might be active conduits for petroleum migration.
98. Distribution of the main accumulations along the model section.
99. Petroleum accumulations were mainly formed in structural traps, such as the Pescada-Arabaiana play.
100. Accumulations inside the Pescada-Arabaiana structure show petroleum (medium oil and smaller proportion of gas) generated by the Pendência and Alagamar/Galinhos Formations
101. This figure shows gaseous hydrocarbon saturations in the Deep Basin Domain and a small liquid hydrocarbon accumulation on the crest of the main basement structure in that region of the section.
102. This figure shows liquid hydrocarbon saturation in the slope Domain on the crest of the main basement structure in that region of the section. The oil is predominantly derived from the Alagamar Formation (Galinhos Mb).
103. The hydrocarbon accumulations along this section are located at great vertical distance of the potential biodegradation zone. The same is not true when the shallow platform and onshore region are considered, as it can be seen on the left side of the section.