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Key Aspects of Basin Modeling to Support Exploration in Present and Future Frontiers

Marcio R. Mello¹, André A. Bender², Nilo C. Azambuja¹, Alain Prinzhofer², David Curry³, Mike Moldowan4, Jeremy Dahl4, Silvana Barbanti5
¹HRT Participações, Rio de Janeiro, Brazil
²HRT Oil and Gas, Rio de Janeiro, Brazil
³HRT America, Houston, Texas, USA
4Biomarker Technology, Sebastopol, California, USA
5IPEXco, Rio de Janeiro, Brazil

In petroleum exploration, the boundaries of the knowledge have been shaped by the characteristics of new geographic locations and by the shift of new concepts. New geographic settings became evident when activities advanced near the oceanic realms as petroleum exploration in continental margins has moved to ultra-deep waters. Additionally, a major step was made with petroleum exploration directed to deep horizons in the continental margin of South Atlantic Basins, which required major technological progress and conceptual acceptance of the source, reservoir quality, trap formation versus charge conditions, and hydrocarbon type in such deep horizons. An additional area that has to be improved is the technical ability of basin modeling to appraise high thermally evolved and high pressure settings. Accurate predictions of pressure and temperature conditions are critical in order to assess oil versus gas prone areas.

This work addresses two cases: one study in a thermally mature setting, Solimões Basin (onshore Brasil) and a second one in a frontier area, Namibian basins (offshore W Africa). There are two main challenges in the Solimões Basin: one is pressure prediction and the second is diagenesis effect reducing porosity and permeability in hydrocarbon reservoirs. Normal pore pressure regime has been impossible to quantify as the bulk of the Carboniferous rocks, overlying the main reservoirs, are characterized by tight rocks as diabase and tight carbonates interlayered with shales and evaporites. High pore pressure should be the case throughout the Paleozoic sedimentary section of the Solimões Basin. The thermal history of Solimões was also quite unusual owing to the high temperature effect of the diabase sills that took place in Juro-Triassic times. Several processes in the Solimões, as thermal maturity, overpressure evolution and the diagenesis effects are crucial to a proper understanding of the processes that controlled hydrocarbon generation, migration and oil and gas quality in the basin, consequently the success of Carboniferous and also the frontier Devonian plays.

The second case is focused on Namibian offshore basins that had their importance highlighted owning to the geological and geochemical characteristics shared with the Giant Sub-Salt hydrocarbon province in Santos Basin. Although the Kudu gas field was the only discovery in the basin, oil-prone Aptian and Barremian source rocks were also identified in the Namibian basins. The use of high-resolution geochemistry analyses oil, condensate and gas from the Kudu area demonstrated similarities with samples from the Santos and Campos basins (Mello et al, 2011), indicating that they share similar petroleum systems. Recently acquired 3D seismic in Namibian basins reveals large- scale structures and potential good plays as channel confined turbidite plays, carbonates platform plays, turbidites plays in toe thrusts, rift plays associated with basement highs and stratigraphic pinchouts in rift grabens. In this work all the important petroleum system elements will be discussed with particular emphasis on the temperature evolution of the basin. The area discussed here in offshore Namibia extends from shallow to deep marine domains and heat flow values will change across the domains owing to rift related heat flow, burial history and thermal properties of the rocks. With basin modeling tools, temperature were predicted in the source and reservoir rocks through time in order to address critical exploration issues as what are the hydrocarbon types, their geographic distribution and timing of petroleum migration into the traps.

The exploration that has been performed in Namibian basins, up to now, used conventional thinking and concluded it is a gas-prone and that was the reason of no exploration effort in the basins for the last 20 years. The use of Basin Modeling together with high-resolution geochemistry, oil slicks detection by satellite images was critical to investigate in a systematic way the efficiency of the petroleum systems and to gain insight to related risks.

AAPG Search and Discovery Article #120098©2013 AAPG Hedberg Conference Petroleum Systems: Modeling the Past, Planning the Future, Nice, France, October 1-5, 2012