First EAGE Eastern Africa Petroleum Geoscience Forum

Hydrocarbon exploration of the East African continental margin has not received the same level of focus as the Atlantic margin. However, since the giant gas discoveries off the coasts of Tanzania and Mozambique, it has been a hotspot of frontier deepwater exploration activity. From Mozambique to Somalia this gigantic continental passive margin basin has been under-explored despite the offshore success stories from the Rovuma, Mozambique and Tanzania basins. The large volumes of gas discovered have raised the question whether any liquid hydrocarbons have been trapped. The large amount of gas might have been generated from oil prone Jurassic or older source rocks. Recently an oil discovery was reported from the Lamu basin, offshore Kenya in 2014. This newly established liquid hydrocarbon play is being studied in detail. Future hydrocarbon exploration campaigns may expand towards the north-eastern Somali basin and into the ultra-deep water areas of the Madagascar channel beyond the Davie ridge, guided by the tectono-sedimentary evolution of the margin. Key risks to the development of such plays will include source rock maturity, related to the nature of the underlying crust and associated heat flow, and regional hydrocarbon migration pathways. This extended abstract intends to summarize key challenges and potential risks in the exploration for oil rather than gas in the East African continental margin basins.

Updating our geological concepts and turning them into meaningful tools to guide our exploration toward discoveries of new types of plays and new petroleum provinces is a major challenge for the oil & gas industry. It demands to revisit our fundamentals (structural, sedimentary and fluids) and start over with a geodynamic approach to the formation of sedimentary basins.

Staying abreast of advances in academic research is paramount as we strive to formulate these innovative concepts and predict new plays. Total strategy is to stay poised to detect and quickly take up the most innovative scientific ideas and pass them on to the field in real time. This will be the key to successful frontier exploration.

In the late sixties large petroleum discoveries were made on the Norwegian continental shelf, a few kilometers outside the west coast of Norway. At that time Norway did not have any direct experience in the petroleum industry, and when it came to petroleum geology and geophysics the knowledge was less than meagre. Norway did, however, have excellent technical skills, top quality higher education, and the universities carried good educational and research programs in general geology and geophysics.

The recent great petroleum discoveries offshore Tanzania can make a big difference and remarkable inspiration for Tanzania, giving a great boost to the society and industry, as well as stimulating higher education. If this opportunity is handled wisely the foundation for future growth can be established.

This setting and my own more than 30 years of Tanzanian geo-project experience, forms the basis for this presentation. Here my personal views, thoughts and ideas on possible ways of organizing geoscience education will be presented, with the aim of being beneficial both for society, academia and the petroleum industry.

This setting and my own more than 30 years of Tanzanian geo-project experience, forms the basis for this presentation. Here my personal views, thoughts and ideas on possible ways of organizing geoscience education will be presented, with the aim of being beneficial both for society, academia and the petroleum industry.

The compilation of a consistent, regional-scale petroleum geological framework for the deep subsurface of Tanzania, both on- and offshore, will give easy and inexpensive access to the accumulated knowledge held by several organizations on the on- and offshore basins and to aid inbetter understanding the geology of Tanzania. A comprehensive and systematic overview of the results of over 60 years of petroleum exploration and research in Tanzania will be published both in paper and digital (GIS) format. It follows successful regional mapping projects in the Netherlands and in northwestern-central Europe.

BG Group entered Tanzania in June 2010 attracted by the possibility of large frontier exploration plays and sizeable licence blocks covering deep to ultra-deep water close to several recent discoveries.

This paper focuses on the exploration activity that has been conducted in offshore Tanzania’s blocks 1 and 4 between 2010 and 2015. The paper will provide examples of the diverse trap types that have been tested, the range of geological ages penetrated with the drill bit and different geological facies identified either through drilling or seismic observation. Emphasis will also be placed on some of the challenges encountered and technological enablers that have been deployed to safely deliver the activities described in a remarkably short timeframe of five years. This exploration activity has delivered sixteen wells with a 100% success rate of encountering hydrocarbons. The activities described have transformed the Tanzanian petroleum story from a “hot spot” of frontier exploration potential to a proven hydrocarbon province holding several TCF of gas spread across multiple plays.

Mzia is a very large gas field, of Cretaceous age, located in the Ruvuma Basin within the Block 1 licence, offshore Tanzania ( Figure 1 ).

In this presentation we will discuss how our understanding of the field has evolved from the initial identification of the prospect on 2D seismic data through to appraisal well drilling, with a particular emphasis on how the depositional setting has influenced the unusual sedimentology of the field.

This talk will provide some of the exploration highlights, explaining successes and failures. We will present how the geological understanding of the area has evolved over time, and demonstrate the impact that state of the art geophysical workflows have in fluid and lithology prediction.

Statoil has drilled 14 wildcat and appraisal wells over the past three years in Block 2, offshore Tanzania. The wells have penetrated numerous gas bearing sandstone reservoirs and aquifers spanning from Early Cretaceous to Neogene age. While the Lower Cretaceous and Tertiary sandstone penetrations are at or near hydrostatic pressure, several Upper Cretaceous sandstones are overpressured. These overpressured units are typified by laterally discontinuous deep marine sandstones encapsulated within thick mudstone. The hypothesis is that overpressure in the Upper Cretaceous sections is related to compaction disequilibrium, which is controlled by the composition of the mudstones. This hypothesis is tested by quantifying and comparing the mudstone mineralogy in the Lower Cretaceous, Upper Cretaceous and Neogene deposits.

X-ray Diffraction (XRD) analyses have been run on samples from 4 exploration wells: Zafarani-1, Lavani-2, Mronge-1 and Giligiliani-1. The first 3 wells are located along the SeaGap fault zone, whereas Giligiliani-1 is in the western part of the block. With the exception of Zafarani-1, the Upper Cretaceous shales have been interpreted to be overpressured, and Upper Cretaceous sandstones in Lavani-2 and Giligiliani-1 had higher than expected pore pressure. XRD analysis will give the composition and proportion of quartz, feldspars, carbonates and total clay, and the distribution of common clay minerals: kaolin, chlorite, illite, smectite, mixed layer clays.

Identifying the controls on the development of overpressured zones will allow for better prediction of their occurrence, improve well planning and further the understanding of hydrocarbon distributions in the basin.

Lake Edward basin forms the extreme southern part of the Albertine graben in southwestern Uganda. This graben forms the northern most part of the western arm of the East African Rift System (EARS).This basin has been explored to understand its paleoclimate, tectonics and depositional history and its petroleum potential.

With these efforts, still its depositional, tectonic history and petroleum potential is less understood.

Dominion (U) limited carried out seismic studies to ascertain its subsurface geology and this led to the drilling of Ngaji-1 well in 2010. This well did not encounter any hydrocarbon shows. Even a potential source rock was not encountered.

However from surface investigations, there is some evidence for the existence of a source rock somewhere in the basin.

From This study, potential reservoir facies, seal/cap facies and traps were encountered.

At this scale of investigations, it is not possible to elucidate the extent of a pre-rift sedimentary basin which appears to host the source rock, and even to ascertain the location of hydrocarbon traps. This could be the subject for further investigations

In this paper results of first time acquisition of IsoTube samples and Fluid Inclusion Data are used to interpret the origin of gasses and migration pathways in the Mozambique Basin. Modelling results point towards the presence of two distinct kitchens, the Zambezi Depression which is high to late mature for dry gas and a not yet described near-shore local kitchen achieving modest maturity for dry gas and condensate.