Avaliação do potencial gerador de hidrocarbonetos na Bacia de Punta del Este (Offshore do Uruguai)
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Data
2022-05-16
Autores
Novo, Rodrigo
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Universidade Estadual Paulista (Unesp)
Resumo
A Bacia de Punta del Este, localizada no offshore do Uruguai, é caracterizada como um aulacógeno resultante do processo de rifteamento do supercontinente Gondwana, desenvolvido no período que abrange do final do Jurássico até meados do início do Cretáceo. Historicamente, os estudos realizados na bacia têm se concentrado principalmente na evolução tectônica e estratigráfica, bem como na análise da existência de potenciais sistemas petrolíferos. Este estudo tem como objetivo geral contribuir para o conhecimento da evolução geológica da Bacia de Punta del Este, visando avaliar o potencial gerador de hidrocarbonetos. Com base na interpretação sismoestratigráfica, na modelagem do fluxo térmico e na evolução geológica e tectônica da bacia, foi possível investigar a sua história térmica e identificar quatro potenciais pods de geração de hidrocarbonetos para uma rocha geradora de idade Barremiano-Aptiano. Para avaliar o potencial de geração dos pods identificados, devido à ausência de dados de poços, foram propostos dois cenários hipotéticos em relação à porcentagem de COT: um primeiro cenário, com %COT=0,6 e um segundo cenário, com %COT=2. Os resultados obtidos sugerem que ambos os cenários apresentam condições favoráveis à geração de hidrocarbonetos, sem diferenças significativas quanto aos períodos de geração de óleo e de gás. No entanto, foram encontradas diferenças relacionadas ao período de expulsão e tipo de hidrocarboneto gerado. Os tipos de fluidos que, potencialmente, teriam sido gerados foram: no primeiro cenário, principalmente black oil para os pods localizados na zona proximal e no centro da bacia, enquanto que nos pods mais distais sobressai-se a geração de gás, além de óleo volátil; e no segundo cenário, principalmente a geração de black oil para todos os pods, sobressaindo-se, no pod mais distal, a geração de gás condensado, além de óleo volátil. A expulsão de hidrocarbonetos teria sido alcançada 20 Ma mais cedo em medía no segundo cenário, e em ambos os cenários a expulsão teria começado primeiro na zona mais distal da bacia, no final do Eocretáceo e começo do Neocretáceo, continuando progressivamente em direção à zona proximal da bacia, no Turoniano-Eoceno. O volume potencial de geração de hidrocarbonetos da Bacia de Punta del Este para uma rocha geradora do Barremiano-Aptiano é de 24.800 milhões de barris de óleo equivalente no primeiro cenário, e de 60.500 milhões de barris de óleo equivalente no segundo cenário. Com base nestes dados, foram propostos dois sistemas petrolíferos especulativos: 1) Barremiano/Aptiano-Neocretáceo (?), que apresenta o timing apropriado para a acumulação de hidrocarbonetos em reservatórios siliciclásticos desenvolvidos, principalmente, no setor central e distal da bacia; 2) Barremiano/Aptiano-Oligoceno/Mioceno (?), que apresenta timing moderado para acumulação de hidrocarbonetos nos reservatórios siliciclásticos desenvolvidos no setor meridional da bacia.
Punta del Este Basin, offshore of Uruguay, is characterized as an aulacogen structure associated with the rifting process of the Gondwana supercontinent, developed during the late Jurassic to mid-Late Cretaceous. Historically, studies carried out in the basin have focused mainly on tectonic and stratigraphic evolution, as well as on the analysis of the speculative petroleum systems. The general objective of this study is to contribute to the knowledge of the geological evolution of Punta del Este Basin, in order to assess the potential for hydrocarbon generation. Based on seismostratigraphic interpretation, heat flow modeling and the geological and tectonic evolution of the basin, it was possible to analyze its thermal history and identify four potential hydrocarbon-generating pods for a Barremian-Aptian source rock. Due to the absence of well data, to assess the generation potential of the identified pods, two hypothetical scenarios (conservative and optimistic) were proposed in relation to the TOC percentage: a first scenario with %TOC=0.6 and a second scenario with %TOC=2. The results obtained suggest that both scenarios present favorable conditions for the generation of hydrocarbons, without significant differences regarding the periods of oil and gas generation. However, differences were found in the timing of expulsion and the type of hydrocarbons generated. Different types of fluids could potentially have been generated. In the first scenario, mainly black oil is generated for the pods located in the proximal zone and in the central part of the basin, while in the more distal pods, gas generation stands out, in addition to volatile oil. In the second scenario, the generation of black oil predominates for all pods, standing out, the generation of condensate gas, in addition to volatile oil in the most distal pod. The expulsion of hydrocarbons would have been achieved 20 Ma earlier on average in the second scenario, and in both scenarios, the expulsion would have started first in the most distal zone of the basin, at the end of the Early Cretaceous and the beginning of the Late Cretaceous, continuing progressively towards the proximal zone of the basin, in the Turonian-Eocene. The potential volume of hydrocarbon generation for a Barremian-Aptian source rock in Punta del Este Basin is 24,800 million barrels of oil equivalent for the first scenario, and 60,500 million barrels of oil equivalent for the second scenario. Based on these data, two speculative petroleum systems were proposed: 1) Barremian/Aptian-Upper Cretaceous (?), which presents an good timing for the accumulation of hydrocarbons in siliciclastic reservoirs deposited, mainly, in the central and distal sectors of the basin; 2) Barremian/Aptian-Oligocene/Miocene (?), which presents a moderate timing for hydrocarbon accumulation in the siliciclastic reservoirs deposited in the southern sector of the basin.
Punta del Este Basin, offshore of Uruguay, is characterized as an aulacogen structure associated with the rifting process of the Gondwana supercontinent, developed during the late Jurassic to mid-Late Cretaceous. Historically, studies carried out in the basin have focused mainly on tectonic and stratigraphic evolution, as well as on the analysis of the speculative petroleum systems. The general objective of this study is to contribute to the knowledge of the geological evolution of Punta del Este Basin, in order to assess the potential for hydrocarbon generation. Based on seismostratigraphic interpretation, heat flow modeling and the geological and tectonic evolution of the basin, it was possible to analyze its thermal history and identify four potential hydrocarbon-generating pods for a Barremian-Aptian source rock. Due to the absence of well data, to assess the generation potential of the identified pods, two hypothetical scenarios (conservative and optimistic) were proposed in relation to the TOC percentage: a first scenario with %TOC=0.6 and a second scenario with %TOC=2. The results obtained suggest that both scenarios present favorable conditions for the generation of hydrocarbons, without significant differences regarding the periods of oil and gas generation. However, differences were found in the timing of expulsion and the type of hydrocarbons generated. Different types of fluids could potentially have been generated. In the first scenario, mainly black oil is generated for the pods located in the proximal zone and in the central part of the basin, while in the more distal pods, gas generation stands out, in addition to volatile oil. In the second scenario, the generation of black oil predominates for all pods, standing out, the generation of condensate gas, in addition to volatile oil in the most distal pod. The expulsion of hydrocarbons would have been achieved 20 Ma earlier on average in the second scenario, and in both scenarios, the expulsion would have started first in the most distal zone of the basin, at the end of the Early Cretaceous and the beginning of the Late Cretaceous, continuing progressively towards the proximal zone of the basin, in the Turonian-Eocene. The potential volume of hydrocarbon generation for a Barremian-Aptian source rock in Punta del Este Basin is 24,800 million barrels of oil equivalent for the first scenario, and 60,500 million barrels of oil equivalent for the second scenario. Based on these data, two speculative petroleum systems were proposed: 1) Barremian/Aptian-Upper Cretaceous (?), which presents an good timing for the accumulation of hydrocarbons in siliciclastic reservoirs deposited, mainly, in the central and distal sectors of the basin; 2) Barremian/Aptian-Oligocene/Miocene (?), which presents a moderate timing for hydrocarbon accumulation in the siliciclastic reservoirs deposited in the southern sector of the basin.
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Palavras-chave
Bacia de Punta del Este, Modelagem de fluxo térmico, Pod de rocha geradora, Sistemas petrolíferos, Punta del Este Basin, Heat flow modelling, Pod of source rock, Petroleum systems