Hamid Seidin - National Iranian Oil Company (NIOC), Iran, University of Bergen (UiB), Norway
Eirik Tvedt - Statoil ASA, Norway
Mohammad Mokhtari - International Institute of Earthquake Engineering and Seismology (IIEES), Iran
Jens Havskov - University of Bergen (UiB), Norway

In sedimentary basins with oil and gas reservoir, local earthquakes could cause some changes in the reservoir performance (production rate) and also difficulties during the drilling. This can have both positive and negative economical consequences. To investigate these effects a preliminary local seismic network was established in December 2005 in the Marun Oil Field area (with lon g history of oil production and some major drilling problems), southwest of Iran. All earthquakes within a radius of about 300 km of the centre of Marun Local Network are being analyzed and the resulting data will be correlated with well data. The Marun Oil Field is situated in a regional compression stress zone on the Marun anticline in the southwestern part of the Zagros orogenic fold and thrust belt. Alluvium, Bakhtiari and Aghajari Formations outcrops can be seen in the area. The database for this study consisted of both 2-D and 3-D Seismic reflection surveys, earthquakes and well data (difficulties encountered during drilling of some wells, historical and present day oil production data). The 2-D seismic survey in the area was conducted 30 years ago, and the 3-D seismic survey has recently being acquired, and it covers main part of the Marun Oil Field. These data has been used to define the main structural elements and their geometry in the study area. So far more than 200 local earthquakes during the 8 months operation of this network have been located. At this presentation, after a review of the main structural elements of the study area, The established seismic local network will be introduced and finally the main results of the ongoing project concerning the present finding of the relationship between both historical (based on existing catalogues) and present day (based on the results of recently established seismic network) and the changes of oil production rate due to seismic activity will be elaborated. Finally the paper will include recommendation for future activity concerning the ongoing project.