The Leviathan Miocene Diapir - A novel insight into the tectonic evolution of the Southern Levant Basin, Eastern Mediterranean

摘要

The Leviathan gas field is the largest accumulation so far discovered in the Southern Levant Basin within the turbiditic Tamar Sand Complex. The discovery of this and other fields in the basin was made possible following acquisition of a vast amount of data since 2000. A consensus has been reached that the basin is dominated by Early Mesozoic extensional blocks related to opening of the Neotethys while Miocene folds formed as a result of its closing. Through the study of geophysical data over the Leviathan gas field and its vicinity, it is suggested that most of what we observe today has been formed since the Early Miocene and that the alleged old blocks are actually intrusive bodies. Their structural timing is accurately constrained by well and seismic data but not their composition, as none has yet been penetrated at any borehole. Mud diapirism is currently assumed, as volcanic or magmatic origin is discarded by magnetic data and salt is yet a remote possibility. The tectonic reconstruction suggests that the Levant Basin developed during the Mesozoic and Early Cenozoic as a set of regional highs and lows that were buried since the Early Tertiary until the Early Miocene by thick conforming sequences including potential reservoir rocks such as the gas-bearing turbiditic sands. It was then subject to an extensional tectonic regime associated with diapirs in the southern part of the basin that formed folded structures while rotational blocks developed to the north, offshore Lebanon. The implications of this tectonic setting on petroleum systems are of prime importance; widespread intrusions may have breached old traps, if they existed. On the other hand they formed potential traps such as the proven gas-filled structures and potentially others at depth. Presence of reservoir rocks and the timing of expulsion and migration from deep sources are the main geological risks.