The West Mediterranean Salt Basin — A Future Petroleum Producing Province?

Roberts, Glyn; Christoffersen, Trond

With the recent exploration successes in the Eastern Mediterranean, attention is now being drawn to other areas of the Mediterranean.

This paper looks at one of those areas which we have named ‘The West Mediterranean Salt Basin' (WMSB) and which lies between the eastern coasts of France & Spain and the west coast of Sardinia and Corsica. It includes the Valencia Trough, North Balearic Basin, Gulf of Lions and the Liguro-Provencal Basin (Roca 2002); and runs southwards into the North Algerian Basin.

The study is based on work carried out by the authors in the planning of a new long offset multi-client seismic survey in the North Balearic Basin. For this, vintage seismic data was obtained and depth conversion carried out.

The depth conversion shows a Messinian (ie Upper Miocene) salt package of typically 1000 to 3000m thickness, overlying up to 3000m of sediments of presumably Oligocene to Miocene age (these lie on Oceanic crust in the main part of the basin and on a rifted Mesozoic continental crust on its margins). The salt is overlain by 2000m plus of younger sediments. The salt has however been affected by gravity sliding and we see classic (Vendeville 2005) areas of upslope extension ie salt pinchout ; midslope translation and downslope contraction(diapirism). These correspond to the three provinces described in the adjacent Gulf of Lions by Ianev et al (2007): Rollover Anticline, Salt Pillows, Salt Diapirs.

In the study area we recognise three petroleum systems:

A) Pliocene/Quaternary - biogenic source:
Post Rift/Post Salt plays: deltaics, turbidites and channel sands in structural and stratigraphic traps.
B) Pre Messinian (Oligocene/Miocene) - sourced from Oligocene/Miocene sapropels(ie organic rich muds - USGS 2004) and shales.
Post Rift/Pre Salt plays: deltaic/ turbidites sealed by Miocene shales and Messinian salt.
Syn Rift: canyon sands and deltaics.
C) Pre Tertiary: on the margins of the Basin.
Pre-Rift plays: possible basement plays as seen in the Casablanca field area - sourced from overlying Oligocene Shales or from the Mesozoic (as in the Amposta field).

DHI's have been recognised in the seismic data and the presence of seeps has been noted (Ianev et al 2007) where the salt has either soled out or been broken up by diapirism.

Work done in the study area shows that the WMSB is undoubtably a petroleum generating province. Plans are underway to acquire new long offset 2-D seismic data in order to evaluate more fully.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013