Ice And Its Potential Impact on Temperature and Pressure of Petroleum Systems: Examples From the Norwegian Barents Sea

Jesper Nielsen

Most of the Barents Sea region was covered by ice frequently during the latest ice ages. These younger ice ages and the associated processes have often been regarded to be the major risk on retention of already entrapped petroleum, particularly in the Norwegian Barents Sea. The higher risk has often been related to the erosion and uplift, which apparently have led to some fault reactivation and leakage observed at the seabed as pockmarks and gas chimneys. By integrating ice ages in basin and petroleum systems modelling, we have explored the possibility of PetroMod 3D models to mimic the resulting temperature and pressure changes relatively deep into the shelf. Any ice sheet lying on the exploitable sedimentary succession results in loading and thereby the potential of raised pressure in the subsurface. Melting of the ice then results in rebounding of the shelf and loss of the pressure. Such geologically fast fluctuations in pressure are mainly controlled by the dynamic ice thicknesses and to which depth the pressure gradients may reach. Shallower reservoir and carrier beds, for example, are more subjected to the pressure gradients introduced by the ice. Consequently the pressures of two phase entrapments, for example, are severely affected by the pressure that may result in the vapour phase to expand and force the liquid phase to spill. In combination with temperature gradients introduced by the ice, there may occur even repeatedly vapour-liquid phase transformations.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013