Bioclastic Turbiditic Reservoirs: San Giorgio, Santa Maria Mare, Sarago Mare Fields (Italy)

Francis E. Heritier, Henri Soudet, Jean-Paul Richert

These three fields and the associated Mormora discovery are located along the coastline of the central Adriatic Sea or on the very proximate shelf south of Ancona. Geologically they belong to the Marches basin. These fields are situated on highly faulted northwest-trending anticlines which are related to a north-south shear zone under the disharmonic cover of late Miocene and early Pliocene shales.

Oil and gas are contained in the Scaglia limestone formation of Late Cretaceous to Paleocene age whose reservoirs consist of high-energy bioclastic grainstones interbedded in open marine chalk deposits, and spread and deposited by turbiditic currents.

The diagenesis of these bioclastic grainstones is closely related to the thickness and composition of the different beds and is chiefly located at the top and bottom of them. It is also related to the fluid content of the reservoir.

Fracturing of these beds under the tectonic stresses is linked to the reservoir's characteristics and to the extension of consolidated facies by diagenesis. This fracturing is responsible for the production behavior of the different wells.

Source rocks are the evaporitic shales of upper Miocene age, mature in the deeper part of the Marches basin under the upper Pliocene olistostromes.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.