--> Forward Hydro-Mechanical Modeling of a Rising Salt Diapir Considering the Effect of Basin Sand Layers

AAPG Annual Convention and Exhibition

Datapages, Inc.Print this page

Forward Hydro-Mechanical Modeling of a Rising Salt Diapir Considering the Effect of Basin Sand Layers

Abstract

We use a forward hydro-mechanical finite-element model to simulate the rise of a salt diapir through a basin and study pore pressure and stresses around it. In our model, a flat salt layer under sea water is buried by dipping sediment layers that are deposited sequentially across the salt layer. We assume a highly permeable layer across the bottom of the basin to represent sand layers in basins. Unlike typical forward models, where the evolution of the salt system is predefined with paleo-geometries, the evolution of the system in our model is controlled by the hydro-mechanics of the salt-basin system. We show that the sand layer transmits significant overpressure laterally from deep sediments far from the diapir to shallow sediments near the diapir, substantially increasing pore pressure near diapir. We also show that this pore pressure increase accelerates the rise of the salt diapir by reducing the shear strength of the diapir roof sediments. This pore pressure increase also causes unloading of sediments at the crest of the sand layer by reducing the effective stresses. Finally, we illustrate that the pore pressure increase brings sediments close to failure, thereby making it hard to control not only pore pressure but also the stability of wellbores near diapirs. Our study offers an insight into the effects basin sand layers on the evolution of salt diapirs, and on pore pressure and stresses near salt diapirs.