Prospectivity

Introduction

  • TGS have acquired over 49,000km of 2D seismic data offshore Madagascar with the majority of this being reprocessed within the last few years
  • Gravity/magnetic data is also available offshore
  • 98 wells have been drilled of which eight are offshore in shallow water
  • TGS have recently completed an interpretation and hydrocarbon prospectivity study on the entire dataset

 

Exploration History

The wells offshore Madagascar have been drilled in shallow water.  Eight of them are available on the western margin, six of which are in the Morondava basin and shelf area:

  • Eponge-1 encountered non-commercial gas in Cretaceous sandstones
  • Gas shows were encountered in most of the other offshore wells

Four wells in the Morondava Basin drilled volcanic structures:

  • Valid structures have not yet been tested, so there is still a lot of potential for future discoveries
  • Onshore there have been oil and gas discoveries including the giant Tsimiroro and the Bemolanga fields, both located ~ 100km from the west coast. Oil shows have been reported in wells throughout the length of the onshore parts of the Morondava and Majunga Basins and others

 

Tectonic History

 Three major events have influenced the formation of the offshore basins of Madagascar in its present form:

  1. Early Jurassic rifting of Madagascar - India from Africa
  2. Middle Jurassic to Aptian movement south along the DFZ transform
  3. Aptian to Late Cretaceous rifting that resulted in the break-up of India and Seychelles from Madagascar

Morondava Basin – Structural Elements

The 2018-19 Licensing Round covers most of the Morondava Basin which can be divided into three main structural elements:

  1. Morondava Shelf
  2. Morondava Basin
  3. Davie Fracture Zone (DFZ)

The seismic data show the DFZ was re-activated during India-Madagascar separation and resulted in large inverted structures. Late Cretaceous igneous rocks extend throughout the Morondava Basin and wedge out against the inverted Mesozoic sediments along the DFZ, thereby dating the inversion event. Therefore, it may be concluded that the DFZ was still active during the Turonian-Santonian. This permits creation of trap structures and migration of hydrocarbons from older source rocks.

 

Morondava Basin – Source Rock Potential

  • Gas shows have been encountered in 3 offshore wells within the Morondava Basin
  • There are two heavy oil fields, the giant Tsimiroro and the Bemolanga, situated roughly adjacent to the shelf and ~ 100km onshore
  • Oil and gas shows have been reported in wells throughout the length of the onshore part of the Morondava Basin
  • The onshore heavy oil fields are sourced from the Triassic Sakamena Formation while further source rock potential exists throughout the Upper and Lower Cretaceous, and the Upper and Middle Jurassic. This is revealed by TOC wt% values detected in Saronanala-1 throughout the Cretaceous and Jurassic intervals. The well sits < 45km onshore in the middle of the Morondava Basin.
  • Oil samples from seabed coring have shown evidence of thermogenic hydrocarbons and multiple oil seeps have been reported offshore Morondava Basin

 

Morondava Basin - Trapping Potential

Morondava Shelf

 

Morondava Basin

 

Davie Fracture Zone (DFZ)

Madagascar Licensing Round 2018