Recent New Discoveries as a Result of Better Understanding the Factors Controlling Hydrocarbon Accumulation in the Sirt Basin, Libya and Future Potential

By

 Talaat K. Barsoum¹

(1) Independant Consultant Geologist, Gerrards Cross, Bucks, England

 As a result of extensive studies, some new exploration concepts have emerged. The application of which led to significant discoveries mainly from Nubian sands in the southeastern part of the Sirt Basin in areas which were considered either fully explored or having no potential and totally down graded. These concepts are: The significance of the bald basement highs for stratigraphic-structural traps as in the giant Messla field It was believed that drilling in the deep troughs in Sirt Basin may yield gas rather than oil due to high geothermal gradient. However, it was proved that the geothermal gradient is actually of moderate value. As the Sirt Basin, being an intercratonic rift basin, almost all known structural traps are well defined horsts at basement level. Applying this concept in part of Gialo and El Lateef oil fields, where oil has been produced from Oligocene sands, but with none of the wells reached any deeper horizon, led to drilling deeper wells with significant discoveries in new reservoirs with larger areal closures. The importance of in-situe oil generation from relatively smaller and shallower troughs.

More than 1.5 billion barrel of oil and 1.6 trillion cubic feet of gas in-place have been disciovered in structural and stratigraphic/structural traps. Several other plays have been delineated with a potential of more than 2.5 billion barrels of oil in-place.

Traditionally, exploration efforts in the Sirt Basin have been concentrated on structural traps, however, there is still an immense potential of hydrocarbon accumulation in stratigraphic/structural and pure stratigraphic traps which are not adequately explored and have hardly been investigated, particularly the latter.