Overpressure Mechanisms and Lateral Fluid Flow in the Taranaki Basin, New Zealand

Abstract

Summary All wells in the Taranaki Basin drilled in excess of 4500 mTVD experienced relatively rapid increases in pore pressure. Hydrocarbon generation and in particular cracking to gas at high maturities, has been interpreted to be contributing to the overpressures encountered, alongside an increase in mudrock volume (reduced permeability). Lateral drainage of overpressures has been demonstrated across the Western Platform and Southern Taranaki Inversion Zone, while lateral transfer is suggested to be occurring in the Tarata Thrust Zone. The poor prediction of both lateral transfer and lateral drainage in wells from across the basin has resulted in numerous well control issues that could have been avoided if knowledge from offset wells was included in the pore pressure prediction and well design.