Print this pageOverpressure Generation and Vertical Transfer in the Sarqala-1 Wildcat, Kurdistan Region of Iraq
Overpressure is a significant drilling hazard in much of the Zagros Fold Belt. Rapid sedimentation throughout the Plio-Pleistocene combined with tectonic compression during formation of the fold belt led to the development of moderate to severe overpressure beneath the regional Miocene Fars evaporite seal. Mud weights in excess of 17 ppg have been required to successfully drill discoveries where overpressure has been encountered. The Sarqala-1 wildcat encountered severe overpressure in younger stratigraphy than ever before seen in N. Iraq. Overpressure was unexpectedly encountered in the clastic alluvial Upper Fars (Injana) formation. Pre-drill basin modelling indicated a very high probability of encountering normal pore pressures. Wireline log data indicates shales in the Fars clastics are normally pressured suggesting overpressure was vertically transferred through hydro-fracturing of the Fars evaporite seal.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009