Monte Pallano Gas Field, Abruzzo Region, Italy Terrain Subsidence Monitoring Requirements

Ronald G. Brown
International, Forest Oil Corp., Denver, CO

Monte Pallano is located in the Region of Abruzzo, Italy, 220 kilometers due east of Rome. It is in the Central Apennine Range that resulted from compression of the Sardinia and Adriatic plates in the Oligocene. It is a fold belt with deformed sedimentary and volcanic units bisected by southwest-dipping thrusts. Extension in late Tertiary resulted in normal faulting.

AGIP drilled a discovery in 1966 followed by three successful wells and three dry holes. The reservoir is a fossiliferous, Upper Cretaceous limestone with porosity averaging 10% and permeability 10 md. The four wells initially flowed 2 to 6 MMcfd after acid cleanup.

At the time, a tragedy occurred in Northern Italy when a slide block fell into the Vajont reservoir. A pulse wave overflowed the dam and destroyed Longarone, a village of 2000 people. The gas field is partly located beneath a Lake held by a 57.50 meter earthen dam. AGIP elected not to produce the field in 1966 due to the Bomba dam proximity. The four wells were plugged and abandoned in 1992. Forest CMI S.p.A. was granted an exploration license containing the field in 2004. The permit required Forest to install monitoring sensors to measure subsidence resulting from gas withdrawal. Forest installed solar powered GPS stations capable of measuring movements to a one-millimeter scale. Upon fulfillment of this requirement, Forest obtained permission to drill two directional wells from a common pad in 2007. The wells re-established production with rates greater than 7 MMcfd. The field has 2500 acres within the closing contour, a GWC at -1112 subsea and a reservoir column of 110 meters. Reserves are placed at 56 Bcfg. Forest is designing a treatment facility and pipeline.

AAPG Search and Discovery Article #90092©2009 AAPG Rocky Mountain Section, July 9-11, 2008, Denver, Colorado