INTRODUCTION

There has been renewed interest in petroleum exploration on- and offshore Lebanon following the recent disclosure of new offshore seismic data and new discoveries offshore Israel and the Levantine margin. The results of recent studies indicating that the sedimentary succession offshore Lebanon may include source and reservoirs rocks similar to those in neighbouring countries have been discussed at recent international conferences and in professional publications (e.g. Breman, 2006; Roberts and Peace, 2007; Gardosh et al., 2009; Lie and Trayfoot, 2009; Montadert et al., 2010). Discoveries offshore Israel (e.g. Noa, Mari-B, Tamar, Dalit and Leviathan) have confirmed the presence of gas accumulations in Pliocene, Miocene and Oligocene sandstones (see www.nobleenergyinc.com).

To date, there has been no commercial development of oil or natural gas in Lebanon. Little exploration has taken place for the past four decades and earlier exploration efforts were unsuccessful. Only seven exploration wells have been drilled in Lebanon, between 1947 and 1967; these failed to encounter oil or gas in commercial volumes, or to penetrate rocks older than the Jurassic Kesrouane Formation which is the oldest unit exposed at the surface. Indications of petroleum, however, have been found both at outcrop and in wells (Dubertret, 1955; Renouard, 1955; Ukla, 1970; Beydoun, 1977a, 1981). The Upper Cretaceous Chekka Formation, which consists of organic-rich mudstones and is well exposed in southern Lebanon, includes two types of asphalt. The first is related to in situ maturation of organic matter; the second is fracture-related and is interpreted to have migrated from a deeper source rock (Al Haddad, 2007). The deeply-buried Triassic succession may possess good source (and reservoir) characteristics, and may also contain evaporitic cap rocks equivalent to those in Syria (Nader and Swennen, 2004b). Recent seismic surveys have drawn attention to the significant potential for hydrocarbon accumulations offshore the northern Lebanese coast(Breman, 2006; Montadert et al., 2010).

This paper is intended to reassess the petroleum prospectivity of Lebanon and to update the petroleum model proposed by Nader and Swennen (2004b). It includes data gathered during early onshore exploration (e.g. Renouard, 1955; Beydoun, 1977a and 1981), more recent studies involving regional correlation and diagenesis (Nader, 2003; Nader and Swennen, 2004a, b) and studies of potential reservoirs and source-rocks (e.g. Doummar, 2005; Al Haddad, 2007). The Upper Cretaceous and Cenozoic rock successions, which have been relatively little studied in the past, were recently subjected to a nannofossil-based stratigraphic investigation which has permitted more precise dating of the structural evolution of Mount Lebanon (Müller et al., 2010). Also discussed are the results of recent offshore seismic surveys (Breman, 2006; Roberts and Peace, 2007; Gardosh et al., 2010).