Petroleum systems and hydrocarbon potential of the Ruvuma Basin, Tanzania

Abstract

Ruvuma Basin is widely recognized across the world for large gas field discoveries, which indicate the presence of gas-prone sources. However, little is known about the basin's source rock's hydrocarbon generation potential, including the distribution of significant petroleum systems. Inferences are often drawn from Permo-Triassic and Jurassic source rocks in Mandawa Basin, Tanzania and Morondava Basin, Madagascar. As a result, knowledge of the basin's potential source rocks is not known. To constrain possible source beds including petroleum systems, this study thoroughly reviewed previous literature coupled with rock eval pyrolysis and vitrinite reflectance analysis on rock cuttings (n = 19) from the Ruvuma Basin's Permo-Triassic, Jurassic, and Cretaceous shales of Lukuledi-1 well.The findings indicate variable petroleum systems with different generation potentialities in the Permo-Triassic, Jurassic, Cretaceous, and Cenozoic intervals. The Permo-Triassic plays sourced hydrocarbons from the matured Permo-Triassic shales of kerogen type II and I, with Total Organic Carbon (TOC) average of 40 %wt, Hydrogen index (HI) average of 286.5 mg HC/g TOC, vitrinite reflectance (Ro%) average of 0.81 with Tmax average of 436 °C capable of oil generation. The Jurassic play systems are charged from matured Jurassic kerogen type III and mixed type II/III shales with TOC∼ 4 %wt, HI∼54.25 mg HC/g TOC, Ro% ∼0.6 and Tmax ∼444 °C capable of gas generation. Cretaceous and the Cenozoic play systems, sourced hydrocarbon from deeper sources because their source rocks are thermally immature with kerogen type III, having TOC ∼0.6 %wt, HI ∼53.6 mg HC/g TOC, Ro% ∼0.3 and Tmax <420 °C capable of gas generation.These results indicate that the Cenozoic play system incorporates hydrocarbons from diverse sources/reservoirs, making it a potential exploration target for future discoveries. These findings necessitate more research to determine migratory patterns, which will result in new ground-breaking discoveries in the basin.